Treatment with once-weekly alendronate 70 mg compared with once-weekly risedronate 35 mg in women with postmenopausal osteoporosis: a randomized double-blind study

Efficacy of risedronate in Japanese male patients with primary osteoporosis

OBJECTIVE

Although osteoporosis in men previously was relatively neglected, bisphosphonates have been strongly suggested as potent therapeutic agents. However, there are few studies on the effects of risedronate in male osteoporosis, especially in Japanese with primary osteoporosis. The aim of our study was to prospectively evaluate the effects of risedronate on bone mineral density (BMD) and bone turnover in Japanese male patients.

METHODS

According to the therapeutic regimen, the subjects were divided into two groups (group A, 22 with risedronate; group B, 10 without risedronate). During a one-year study duration, we measured bone-specific alkaline phosphatase (BAP) and serum N-terminal telopeptide of type I collagen (NTx) every 3 months, and BMD at 7 sites by dual-energy X-ray absorptiometry every 6 months.

PATIENTS

The subjects were 32 Japanese male patients with untreated primary osteoporosis.

RESULTS

In group A, but not in group B, BMD was significantly increased at the lumbar spine both at 6 months and 12 months, and at the femoral neck at 12 months, compared with baseline. Likewise, in group A, but not in group B, both BAP and NTx were significantly decreased at all time points measured (3 months, 6 months, and 12 months), compared with baseline.

CONCLUSION

These results confirmed the beneficial effects of risedronate upon increasing BMD and reducing bone turnover markers in Japanese male patients with primary osteoporosis, comparable to those previously reported in postmenopausal patients with osteoporosis.

Once-monthly oral ibandronate compared with weekly oral alendronate in postmenopausal osteoporosis: results from the head-to-head MOTION study

OBJECTIVE

Oral ibandronate 150 mg is the first bisphosphonate approved for once-monthly treatment of postmenopausal osteoporosis. To investigate whether once-monthly ibandronate 150 mg increases lumbar spine and total hip bone mineral density (BMD) to the same degree as weekly alendronate 70 mg.

RESEARCH DESIGN AND METHODS

This was a 12-month, randomised, multinational, multicentre, double-blind, double-dummy, parallel-group, non-inferiority trial, conducted in 65 centres in North America, Latin America, Europe and South Africa. The study included postmenopausal women, mean lumbar spine (L2-L4) BMD T-score < -2.5 and > or = -5.0. Patients received either ibandronate 150 mg once monthly or alendronate 70 mg once weekly.

MAIN OUTCOME MEASURES

Co-primary efficacy endpoints were 12-month change (%) from baseline in mean lumbar spine and total hip BMD. Changes (%) from baseline in trochanter and femoral neck BMD were also evaluated. Adverse events were monitored throughout. Once-monthly ibandronate was considered non-inferior to weekly alendronate if the lower boundary of the one-sided 97.5% confidence interval (CI) (or two-sided 95% CI) was > or = -1.41% for lumbar spine and > or = -0.87% for total hip.

RESULTS

Mean relative 12-month changes were 5.1% and 5.8% (95% CI for difference, -1.13, -0.23) in lumbar spine and 2.9% and 3.0% (95% CI for difference, -0.38, 0.18) in total hip BMD with once-monthly ibandronate and weekly alendronate, respectively; meeting the non-inferiority criteria at both sites. Gains in trochanter and femoral neck BMD were similar with both treatments. Both regimens were well tolerated.

TRIAL REGISTRATION

The MOTION study is registered with the International Federation of Pharmaceutical Manufacturers and Associations trial portal, under the ID number MM17385.

CONCLUSIONS

Once-monthly ibandronate was shown to be clinically comparable to weekly alendronate at increasing BMD after 12 months in both the lumbar spine and total hip.

Bisphosphonates and osteomyelitis of the jaw: a pathogenic puzzle

The maxillary and mandibular bones undergo high-turnover remodeling to maintain mechanical competence. Common dental or periodontal diseases can increase local bone turnover. Bisphosphonates (BPs) accumulate almost exclusively in skeletal sites that have active bone remodeling. The maxillary and mandibular bones are preferential sites for accumulation of BPs, which become buried under new layers of bone and remain biologically inactive for a long time. Surgical odontostomatological procedures create open bony wounds that heal quickly and without infection, as a result of activation of osteoclasts and subsequently osteoblasts. Once BPs are removed from the bone via activation of osteoclasts after a tooth extraction or a periodontal procedure, they induce osteoclast apoptosis. This inhibition of osteoclast bone resorption impairs bone wound healing because of decreased production of cytokines derived from the bone matrix, and the bone is exposed to the risk of osteomyelitis and necrosis. The pathogenic relationship between BPs and osteonecrosis of the jaw is unclear, but there is evidence to indicate an association between high-dose BP treatment and exposure to dental infections or oral surgical procedures. A better knowledge of the interactions between BPs and jaw and maxillary bone biology will improve clinical and therapeutic approaches.

Basic and clinical aspects of osteoporosis in inflammatory bowel disease

Low bone mineral density and the increased risk of fracture in gastrointestinal diseases have a multifactorial pathogenesis. Inflammatory bowel disease (IBD) has been associated with an increased risk of osteoporosis and osteopenia and epidemiologic studies have reported an increased prevalence of low bone mass in patients with IBD. Certainly, genetics play an important role, along with other factors such as systemic inflammation, malnutrition, hypogonadism, glucocorticoid therapy in IBD and other lifestyle factors. At a molecular level the proinflammatory cytokines that contribute to the intestinal immune response in IBD are known to enhance bone resorption. There are genes influencing osteoblast function and it is likely that LRP5 may be involved in the skeletal development. Also the identification of vitamin D receptors (VDRs) and some of its polymorphisms have led to consider the possible relationships between them and some autoimmune diseases and may be involved in the pathogenesis through the exertion of its immunomodulatory effects during inflammation. Trying to explain the physiopathology we have found that there is increasing evidence for the integration between systemic inflammation and bone loss likely mediated via receptor for activated nuclear factor kappa-B (RANK), RANK-ligand, and osteoprotegerin, proteins that can affect both osteoclastogenesis and T-cell activation. Although glucocorticoids can reduce mucosal and systemic inflammation, they have intrinsic qualities that negatively impact on bone mass. It is still controversial if all IBD patients should be screened, especially in patients with preexisting risk factors for bone disease. Available methods to measure BMD include single energy x-ray absorptiometry, DXA, quantitative computed tomography (QCT), radiographic absorptiometry, and ultrasound. DXA is the establish method to determine BMD, and routinely is measured in the hip and the lumbar spine. There are several treatments options that have proven their effectiveness, while new emergent therapies such as calcitonin and teriparatide among others remain to be assessed.

Risedronate did not block the maximal anabolic effect of PTH in aged rats

The study was designed to investigate if pre-treating rats with a therapeutic equivalent dose of risedronate blunted the anabolic effects of PTH, and whether a withdrawal period prior to PTH treatment would alter any effect of risedronate on PTH treatment. Skeletally mature rats were treated for 18 weeks with vehicle, risedronate, or risedronate for 8 weeks followed by vehicle for 10 weeks (withdrawal period). At the end of this period, animals were treated for a further 12 weeks with PTH or PTH vehicle. Trabecular and cortical bone mass were monitored by serial pQCT, or by DXA and microCT. Bone histomorphometry was performed on the proximal tibiae and tibial shafts for bone turnover parameters at week 40. Risedronate alone moderately increased while PTH alone markedly increased trabecular bone mass at the proximal tibial (35% and 200%, respectively) and lumbar vertebral body (14% and 36%, respectively). The maximum bone gains were similar with and without pretreatment with risedronate as compared to the PTH alone. Continuous administration of risedronate for 18 weeks prior to PTH treatment had lower percentage increases in proximal tibial BMD during the first 8 weeks of PTH treatments, and had lower active bone forming surface and bone formation rates after being treated with PTH 12 weeks as compared to the PTH alone group. However, with the 10-week withdrawal period, risedronate did not blunt the stimulatory effect of PTH on osteoblast activity as shown by similar bone formation rates as with PTH alone. Our findings suggest that while risedronate pretreatment may slow the bone anabolic response to PTH, a withdrawal period prior to PTH treatment allows osteoblastic activity to respond normally to PTH stimulation.

Long-term experience with alendronate in the treatment of osteoporosis

Osteoporosis is characterised by increased bone turnover, low bone mass and impaired bone microarchitecture, leading to increased fracture risk. Effective anticatabolic therapies decrease fracture risk by reducing the rate of bone turnover, thereby maintaining bone microarchitecture and increasing bone mineral density. At present, potent oral bisphosphonates, such as alendronate (FOSAMAX; Merck & Co.), are preferred for the treatment of osteoporosis. Long-term clinical trial data demonstrate that alendronate is effective and generally well tolerated. Results from head-to-head studies and meta-analyses suggest that alendronate is more effective than certain other anticatabolic agents in the treatment of patients with osteoporosis.

Evaluation of 41calcium as a new approach to assess changes in bone metabolism: effect of a bisphosphonate intervention in postmenopausal women with low bone mass

A new technique was evaluated to identify changes in bone metabolism directly at high sensitivity through isotopic labeling of bone Ca. Six women with low BMD were labeled with 41Ca up to 700 days and treated for 6 mo with risedronate. Effect of treatment on bone could be identified using 41Ca after 4-8 wk in each individual.

INTRODUCTION

Isotopic labeling of bone using 41Ca, a long-living radiotracer, has been proposed as an alternative approach for measuring changes in bone metabolism to overcome current limitations of available techniques. After isotopic labeling of bone, changes in urinary 41Ca excretion reflect changes in bone Ca balance. The aim of this study was to validate this new technique against established measures. Changes in bone Ca balance were induced by giving a bisphosphonate.

MATERIALS AND METHODS

Six postmenopausal women with diagnosed osteopenia/osteoporosis received a single oral dose of 100 nCi 41Ca for skeleton labeling. Urinary 41Ca/40Ca isotope ratios were monitored by accelerator mass spectrometry up to 700 days after the labeling process. Subjects received 35 mg risedronate per week for 6 mo. Effect of treatment was monitored using the 41Ca signal in urine and parallel measurements of BMD by DXA and biochemical markers of bone metabolism in urine and blood.

RESULTS

Positive response to treatment was confirmed by BMD measurements, which increased for spine by +3.0% (p = 0.01) but not for hip. Bone formation markers decreased by -36% for bone alkaline phosphatase (BALP; p = 0.002) and -59% for procollagen type I propeptides (PINP; p = 0.001). Urinary deoxypyridinoline (DPD) and pyridinoline (PYD) were reduced by -21% (p = 0.019) and -23% (p = 0.009), respectively, whereas serum and urinary carboxy-terminal teleopeptides (CTXs) were reduced by -60% (p = 0.001) and -57.0% (p = 0.001), respectively. Changes in urinary 41Ca excretion paralleled findings for conventional techniques. The urinary 41Ca/40Ca isotope ratio was shifted by -47 +/- 10% by the intervention. Population pharmacokinetic analysis (NONMEM) of the 41Ca data using a linear three-compartment model showed that bisphosphonate treatment reduced Ca transfer rates between the slowly exchanging compartment (bone) and the intermediate fast exchanging compartment by 56% (95% CI: 45-58%).

CONCLUSIONS

Isotopic labeling of bone using 41Ca can facilitate human trials in bone research by shortening of intervention periods, lowering subject numbers, and having easier conduct of cross-over studies compared with conventional techniques.

Is a change in bone mineral density a sensitive and specific surrogate of anti-fracture efficacy?

Anti-resorptive agents perturb steady state remodeling; they suppress, but do not abolish, the birth rate of new basic multicellular units (BMUs). In doing so, remodeling goes to completion with bone formation in the many BMUs created before treatment but now with fewer resorption cavities appearing concurrently. As a result, cortical porosity and trabecular stress concentrators decrease reducing bone fragility. From this improved bone strength, steady state is re-established at a slower remodeling rate that again produces bone fragility but more slowly as fewer new BMUs, each with a less negative BMU balance, produce cortical thinning and porosity, trabecular thinning and loss of connectivity while bone fragility progresses rapidly in controls. Thus, the fracture risk reduction--the incidence of fractures in patients treated with an anti-resorptive agent relative to the incidence in controls--is the net effect of the slowing or partial reversal of fragility and then reduced progression of structural abnormalities in treated patients and continued structural decay in controls. Although some morphological features in treated patients and controls may be captured in the bone mineral density (BMD) measurement, many are not. The early increase in BMD is largely determined by the pre-treatment remodeling rate whereas the later and more modest BMD increase is a function of the degree of suppression of remodeling and secondary mineralization. When pre-treatment remodeling rate is low, the increase in BMD is small but the fracture risk reduction (relative to controls with comparable baseline characteristics) is no different to that in patients with high baseline remodeling (relative to their controls) and a greater BMD increase. Therefore, a small increase in BMD does not mean treatment has failed and a large increase in BMD is not indicative of a greater fracture risk reduction.

Bisphosphonates

Osteoporosis is the result of bone loss due to an imbalance in bone turnover such that bone resorption exceeds bone formation. Bisphosphonates are potent inhibitors of osteoclast activity that reduce bone turnover and re-establish the balance between bone resorption and formation. In clinical studies, several bisphosphonates prevent bone loss, preserve bone structure, improve bone strength and, in patients with osteoporosis, substantially reduce fracture risk. They are effective in multiple clinical settings including postmenopausal osteoporosis, low bone mass in men and drug-induced bone loss. Intermittent oral dosing and intravenous administration are more convenient than the original daily dosing regimen. These drugs are generally well tolerated and have an excellent safety profile in that serious side effects are uncommon. Potent bisphosphonates are generally the preferred treatment option for most patients with or at risk for osteoporosis.

Clinical evaluation of novel bisphosphonate dosing regimens in osteoporosis: The role of comparative studies and implications for future studies

BACKGROUND

Daily nitrogen-containing bisphosphonates have shown antifracture efficacy in many studies of postmenopausal osteoporosis. However, current dosing schedules are often inconvenient or impractical for patients. Efforts to reduce dosing frequency to improve adherence (ie, compliance and persistence), and therefore treatment outcomes, are ongoing. Although a number of trial designs can be used to consider the efficacy of therapy, comparing the efficacy of different regimens should only be undertaken in purposefully designed head-to-head studies.

OBJECTIVE

This article summarizes the design and conduct of clinical studies that have investigated alternative bisphosphonate regimens and those that have directly compared different approved bisphosphonates. It also explores the implications for future studies of postmenopausal osteoporosis treatment.

METHODS

Using the terms bisphosphonate, daily, weekly, and monthly, a search (completed in 2006) of the PubMed database was conducted to identify primary English-language publications of pertinent studies comparing either novel with established regimens of the same bisphosphonates or different established bisphosphonates.

RESULTS

The first option is the equivalence or noninferiority bridging study for comparison of new treatment regimens versus the established regimen of the same bisphosphonate, known as the active comparator. Four such studies have led to the registration of novel bisphosphonate dosing regimens designed to provide easier dosing alternatives for patients. The second option is the active comparator study, which compares one bisphosphonate with the most prescribed weekly bisphosphonate. Weekly dosed oral alendronate has previously been shown to be superior (for bone mineral density gains) to daily and weekly dosed oral risedronate. An ongoing noninferiority study, Monthly Oral Therapy with Ibandronate for Osteoporosis Intervention, is comparing weekly alendronate with ibandronate, a monthly oral bisphosphonate.

CONCLUSIONS

The exploration of new dosing schedules and formulations aims to identify the optimal bisphosphonate regimen for postmenopausal osteoporosis. To achieve this, careful consideration must be given to the choice of a scientifically valid study design that effectively, and ethically, meets the study objectives. Given the concerns regarding placebo-controlled antifracture studies, 2 alternative study designs should be considered, both using validated surrogate end points (bone mineral density and biochemical markers of bone turnover) as the principal mode of assessment.

Treatment with alendronate plus calcium, alendronate alone, or calcium alone for postmenopausal low bone mineral density

OBJECTIVE

Bisphosphonates such as alendronate are widely used for postmenopausal osteoporosis. Supplemental calcium is also generally recommended. This trial directly compares alendronate to supplemental calcium and examines the effect of calcium supplementation on alendronate treatment.

METHODS

This 2-year, randomized, double-blind, multicenter trial enrolled healthy, postmenopausal women with low bone mineral density (BMD). Patients with a dietary calcium intake > or = 800 mg/day received daily vitamin D 400 IU and alendronate 10 mg/calcium-placebo, alendronate 10 mg/elemental calcium 1000 mg, or alendronate-placebo/calcium 1000 mg (2:2:1). Endpoints included BMD, bone turnover markers (BTMs), and adverse events.

RESULTS

Randomized patients (N = 701) were an average of 20.4 years postmenopausal. After 24 months, increases in lumbar spine BMD differed significantly between patients receiving calcium alone (0.8%) and either alendronate alone (5.6%) or alendronate + calcium (6.0%) (p < 0.001). Significant differences were also seen at the trochanter and femoral neck (p < 0.001). BTMs were significantly lower with alendronate-containing treatments than calcium alone (p < 0.001). Addition of calcium supplementation to alendronate did not significantly increase BMD compared to alendronate alone (p = 0.29 to 0.97), but did result in a statistically significant, though small, additional reduction in urinary NTx. Adverse events were similar among treatment groups. Limitations include no assessment of vitamin D levels and a discontinuation rate of approximately 30%, although discontinuation rates were similar among treatment groups.

CONCLUSIONS

In postmenopausal women with a daily intake of > or =800 mg calcium and 400 IU vitamin D, 24-month treatment with alendronate 10 mg daily with or without calcium 1000 mg resulted in significantly greater increases in BMD and reduction of bone turnover than supplemental calcium alone. Addition of supplemental calcium to alendronate treatment had no effect on BMD and resulted in a small, though statistically significant, additional reduction in NTx.

Emerging issues with bisphosphonates

Bisphosphonates are the most commonly used agents in the management of metabolic bones diseases. Despite their established therapeutic value, a number of points of uncertainty remain, particularly in connection with their optimal long-term use. It is likely that definitive clinical trial data will not become available to resolve these questions, so careful clinical observation and caution are needed in patients who require treatment over periods of more than 10 years.

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.

Clinical aspects of obesity in the gynecological endocrinologicaly practice

Obesity is epidemic of 21st century, its visceral form is associated with increased risk for type 2 diabetes, cardiovascular disease, hypertension and increased mortality due to consequences of the disease. This type of obesity is a common diagnostic and therapeutic problem in gynecological practice. This especially concerns polycystic ovary disease, in which this type of obesity with its metabolic consequences is one of the important factors in etiology and additionally may lead to remote metabolic and cardiovascular problems. Another group of women in which this type of obesity plays an important role are climacteric women in whom redistribution of adipose tissue with increase in visceral fat deposit occurs. On the basis of current viewpoints and own experiences, the authors propose a diagnostic-therapeutic algorithm in women with visceral obesity and polycystic ovary disease or climacteric period. In case with cardiovascular risk factors (waist circumference over than 80cm, serum triglycerides over 1.7mmol/l, HDL cholesterol lower than 1.0mmol/l, blood pressure over 130/85mmHg and fast serum glucose levels over 100mg/dl) the therapeutic model focuses on the recognize risk factors. It must be considered that diet and physical activity play a very important role in the therapy.

Recent developments in bisphosphonate therapy

OBJECTIVE

To provide a review of current developments in bisphosphonates indicated for the treatment of several rheumatologic conditions, including postmenopausal and glucocorticoid-induced osteoporosis.

METHODS

This review summarizes the pathology, diagnosis, and treatment of both postmenopausal and glucocorticoid-induced osteoporosis and examines the results of current clinical trials of the newest oral and intravenous formulations of nitrogen-containing bisphosphonates. We discuss important adverse events, including upper gastrointestinal symptoms and osteonecrosis of the jaw. Additionally, we explore methods that may improve patient adherence to bisphosphonate therapy, which is currently suboptimal.

RESULTS

Clinical studies have shown that oral bisphosphonates are efficacious in increasing bone mineral density and reducing risk of fracture. Despite concerns of upper gastrointestinal irritation, most of the newer oral bisphosphonates display a safety profile similar to placebo. Many of the newest formulations offer patients a choice in both dosing frequency and method of administration (either oral or intravenous).

CONCLUSIONS

Nitrogen-containing bisphosphonates are important therapeutic options for the prevention and treatment of osteoporosis.

Drug insight: Existing and emerging therapies for osteoporosis

Osteoporosis is a major public health problem that is characterized by microarchitectural deterioration, low bone mass, and increased risk of fractures. Currently, many women and men affected with this disease are not diagnosed or treated. As osteoporosis is often clinically silent, risk-factor assessment and measurement of BMD are needed to identify those who may benefit from osteoporosis therapy. Although adequate daily intake of calcium and vitamin D, and regular weight-bearing exercise are important for skeletal health, they are not adequate treatments for individuals with osteoporosis. Therapies approved for treatment and/or prevention of osteoporosis in the United States include oral bisphosphonates (alendronate, ibandronate and risedronate), calcitonin, estrogens, teriparatide (parathyroid hormone fragment [1-34]), and raloxifene. For most patients, oral bisphosphonates are the treatment of choice, given the large-scale randomized-trial data demonstrating efficacy in fracture reduction, although bisphosphonates that reduce spine and nonspine fractures (e.g. alendronate and risedronate) are preferred. For high-risk patients (those with very low bone density, or with fractures), teriparatide therapy for 2 years should be considered. The treatment paradigm for osteoporosis will evolve further as promising new treatments progress through clinical development.

Intermittent Bisphosphonate Therapy in Postmenopausal Osteoporosis

Bisphosphonates are the most widely prescribed drugs in osteoporosis today. They have unequivocally shown their ability to reduce fracture rate at the spine (alendronic acid, risedronic acid, ibandronic acid) and at the hip (alendronic acid and risedronic acid). However, their dosage and administration procedures and the adverse reactions induced by their oral intake are responsible for low adherence. Therefore, intermittent regimens have been developed. Weekly alendronic acid and risedronic acid provide similar benefits, in terms of bone mineral density (BMD) and changes in biochemical markers, as those seen with their daily formulations. Ibandronic acid has been shown to reduce vertebral fractures when given intermittently. Ibandronic acid given orally monthly and intravenously every 2 or 3 months provides increases in BMD similar to the daily formulation. Yearly intravenous infusions of zoledronic acid are currently being evaluated for their ability to reduce fractures. If the efficacy and safety of bisphosphonates given at administration intervals longer than weekly are confirmed, this might significantly improve patient adherence and long-term outcomes of bisphosphonate treatment in postmenopausal osteoporosis.

Changes in bone resorption markers among Japanese patients with postmenopausal osteoporosis treated with alendronate and risedronate

We compared the abilities of alendronate and risedronate to reduce levels of urinary cross-linked N-telopeptides of type I collagen (NTX) in Japanese postmenopausal women. The patients were randomly divided into two groups (alendronate, 5 mg/day, n = 61; risedronate, 2.5 mg/day, n = 60). All patients had taken all medication prescribed for the first month and at least 90% of that prescribed for each of the following 6 months. Urinary NTX was measured at baseline, as well as at 1 and 6 months after starting treatment. According to the guidelines of the Japan Osteoporosis Society, the minimum significant change (MSC) for urinary NTX is defined as a 35% decrease from baseline and the cutoff level for a high risk of future fracture is 54.3 nmol bone collagen equivalent (BCE)/mmol.Cr. The NTX reduction rates at 1 and 6 months were greater with alendronate than with risedronate, but the difference was not significant. The rate of patients with a reduction in the MSC at 1 month was greater with alendronate than with risedronate, but the difference did not reach significance. Alendronate reduced NTX at 1 month significantly more in patients with a high risk of fracture than risedronate, but the difference was no longer significant at 6 months. The rate of MSC did not significantly differ between the two groups. In conclusion, alendronate decreases bone resorption markers more obviously and rapidly than risedronate, especially in high risk for fracture, but not significantly according to the guidelines of the Japan Osteoporosis Society.

A highly potent inhibitor of cathepsin K (relacatib) reduces biomarkers of bone resorption both in vitro and in an acute model of elevated bone turnover in vivo in monkeys

Cathepsin K is an osteoclast-derived cysteine protease that has been implicated as playing a major role in bone resorption. A substantial body of evidence indicates that cathepsin K is critical in osteoclast-mediated bone resorption and suggests that its pharmacological inhibition should result in inhibition of bone resorption in vivo. Here we report the pharmacological characterization of SB-462795 (relacatib) as a potent and orally bioavailable small molecule inhibitor of cathepsin K that inhibits bone resorption both in vitro in human tissue and in vivo in cynomolgus monkeys. SB-462795 is a potent inhibitor of human cathepsins K, L, and V (K(i, app)=41, 68, and 53 pM, respectively) that exhibits 39-300-fold selectivity over other cathepsins. SB-462795 inhibited endogenous cathepsin K in situ in human osteoclasts and human osteoclast-mediated bone resorption with IC50 values of approximately 45 nM and approximately 70 nM, respectively. The anti-resorptive potential of SB-462795 was evaluated in normal as well as medically ovariectomized (Ovx) female cynomolgus monkeys. Serum levels of the C- and N-terminal telopeptides of Type I collagen (CTx and NTx, respectively) and urinary levels of NTx were monitored as biomarkers of bone resorption. Administration of SB-462795 to medically ovariectomized or normal monkeys resulted in an acute reduction in both serum and urinary markers of bone resorption within 1.5 h after dosing, and this effect lasted up to 48 h depending on the dose administered. Our data indicate that SB-462795 potently inhibits human cathepsin K in osteoclasts, resulting in a rapid inhibition of bone resorption both in vitro and in vivo in the monkey. These studies also demonstrate the therapeutic potential of relacatib in the treatment of postmenopausal osteoporosis and serves to model the planned clinical trials in human subjects.

Prevention of bone loss in survivors of breast cancer: A randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Few data are available on the safety and efficacy of once-weekly oral bisphosphonate therapy in breast cancer survivors.

OBJECTIVE

Our objective was to determine whether risedronate, 35 mg weekly, is efficacious and safe in preventing bone loss associated with chemotherapy-induced menopause.

DESIGN

The study was a randomized, double-blind, placebo-controlled clinical trial over 12 months.

SETTING AND PARTICIPANTS

Participants included 87 newly postmenopausal women with status post chemotherapy, recruited from a breast cancer clinic in an academic medical center.

INTERVENTION

Participants were randomly assigned to receive risedronate 35 mg/wk or placebo.

MAIN OUTCOME MEASURES

The primary outcomes were the 12-month changes in spine and hip bone mineral density. Secondary outcomes included changes in markers of bone resorption (urine N-telopeptide cross-linked collagen type I) and formation (osteocalcin, N-terminal propeptide of type I procollagen, and bone-specific alkaline phosphatase).

RESULTS

After 12 months, bone mineral density increased by 1.2% at the spine and 1.3% at the hip in women on risedronate vs. significant decreases for women in the placebo group of 0.9% at the spine and 0.8% at the hip (P < 0.01, difference between groups). N-telopeptide cross-linked collagen type I, a marker of bone resorption, decreased by 19.3%, and N-terminal propeptide of type I procollagen, a marker of bone formation, decreased by 26.6% in participants on active therapy compared with increases in the control group. Risedronate was well tolerated, and the retention rate was 95% at 1 yr.

CONCLUSIONS

Risedronate once weekly prevented bone loss and reduced bone turnover in women with breast cancer treated with chemotherapy. Early measures to prevent bone loss should be considered in this cohort of breast cancer survivors.

Effectiveness of bisphosphonates on nonvertebral and hip fractures in the first year of therapy: the risedronate and alendronate (REAL) cohort study

INTRODUCTION

Randomized clinical trials have shown that risedronate and alendronate reduce fractures among women with osteoporosis. The aim of this observational study was to observe, in clinical practice, the incidence of hip and nonvertebral fractures among women in the year following initiation of once-a-week dosing of either risedronate or alendronate.

METHODS

Using records of health service utilization from July 2002 through September 2004, we created two cohorts: women (ages 65 and over) receiving risedronate (n = 12,215) or alendronate (n = 21,615). Cox proportional hazard modeling was used to compare the annual incidence of nonvertebral fractures and of hip fractures between cohorts, adjusting for potential differences in risk factors for fractures.

RESULTS

There were 507 nonvertebral fractures and 109 hip fractures. Through one year of therapy, the incidence of nonvertebral fractures in the risedronate cohort (2.0%) was 18% lower (95% CI 2% - 32%) than in the alendronate cohort (2.3%). The incidence of hip fractures in the risedronate cohort (0.4%) was 43% lower (95% CI 13% - 63%) than in the alendronate cohort (0.6%). These results were consistent across a number of sensitivity analyses.

CONCLUSION

Patients receiving risedronate have lower rates of hip and nonvertebral fractures during their first year of therapy than patients receiving alendronate.

Postmenopausal osteoporosis: an update on current and future therapeutic options

Recent advances in osteoporosis have dramatically changed the management and treatment of this disease. This article reviews the safety and efficacy of US FDA-approved drugs for prevention and treatment of postmenopausal osteoporosis, as well as studies on combination, sequential or intermittent use of these agents. A review of promising agents for osteoporosis therapy is provided.

New mechanisms and targets in the treatment of bone fragility

Bone modelling and remodelling are cell-mediated processes responsible for the construction and reconstruction of the skeleton throughout life. These processes are chiefly mediated by locally generated cytokines and growth factors that regulate the differentiation, activation, work and life span of osteoblasts and osteoclasts, the cells that co-ordinate the volumes of bone resorbed and formed. In this way, the material composition and structural design of bone is regulated in accordance with its loading requirements. Abnormalities in this regulatory system compromise the material and structural determinants of bone strength producing bone fragility. Understanding the intercellular control processes that regulate bone modelling and remodelling is essential in planning therapeutic approaches to prevention and treatment of bone fragility. A great deal has been learnt in the last decade. Clinical trials carried out exclusively with drugs that inhibit bone resorption have identified the importance of reducing the rate of bone remodelling and so the progression of bone fragility to achieved fracture reductions of approx. 50%. These trials have also identified limitations that should be placed upon interpretation of bone mineral density changes in relation to treatment. New resorption inhibitors are being developed, based on mechanisms of action that are different from existing drugs. Some of these might offer resorption inhibition without reducing bone formation. More recent research has provided the first effective anabolic therapy for bone reconstruction. Daily injections of PTH (parathyroid hormone)-(1–34) have been shown in preclinical studies and in a large clinical trial to increase bone tissue mass and reduce the risk of fractures. The action of PTH differs from that of the resorption inhibitors, but whether it is more effective in fracture reduction is not known. Understanding the cellular and molecular mechanisms of PTH action, particularly its interactions with other pathways in determining bone formation, is likely to lead to new therapeutic developments. The recent discovery through mouse genetics that PTHrP (PTH-related protein) is a crucial bone-derived paracrine regulator of remodelling offers new and interesting therapeutic targets.

Osteoporosis

Osteoporosis, as defined by the National Osteoporosis Foundation, is a disease that is characterized by low bone mass and structural deterioration of bone tissue, which leads to bone fragility and an increased susceptibility to fractures. Aging is only one factor that contributes to the development of osteoporosis. Genetics, suboptimal nutrition, deficiency of calcium and vitamin D, lifestyle, smoking, decrease in sex hormone production, and medications also contribute to skeletal fragility. Osteoporotic fractures are a frequent and important cause of disability and medical costs worldwide. Fortunately, osteoporotic fractures are preventable. Several guidelines for the prevention, screening, diagnosis, and management for osteoporosis have been established. Although some are consistent and similar, others are not.

Effects of alendronate and risedronate on bone mineral density and bone turnover markers in late postmenopausal women with osteoporosis

This study was undertaken to compare the effects of alendronate and risedronate on bone mineral density (BMD) and bone turnover markers (BTMs) in late postmenopausal women with osteoporosis. Thirty women older than 60 y of age were randomly assigned to receive alendronate 10 mg (n=16) or risedronate 5 mg (n=14) on a daily basis. The patients were followed every 3 mo for 12 mo. BMD measurements were taken at baseline and at the end of the study, and BTMs were measured at 3-mo intervals. By the end of the study, there were statistically significant increases in BMD in both groups at all sites at which they were measured (P<.001). However, these differences were not statistically significant between groups. By the end of the study, all BTMs had decreased significantly and to a similar extent in both groups. The most significant change was observed in the third month of the study. A negative correlation was noted between percentage change in bonespecific alkaline phosphatase and femoral neck BMD (r=-0.467). This study reported no difference between the 2 drugs in their effects on BMD and BTMs.

Hip and non-spine fracture risk reductions differ among antiresorptive agents: Evidence from randomised controlled trials

A number of antiresorptive agents reduce the risk of vertebral fractures, but few have shown consistent effects on hip and other non-spine fractures. Meta-analysis provides a more precise estimate than individual trials when results are consistent across pooled trials. Earlier meta-analyses summarised the results for vertebral and non-spine fractures. New data have emerged for hormone therapy (HT), alendronate (ALN), risedronate (RIS) and ibandronate (IBN). We surveyed recent reports of randomised, placebo-controlled trials with non-spine and/or hip fracture data, and used meta-analysis where appropriate to test for heterogeneity and derive pooled estimates. The magnitude of effect on hip fracture appears to be similar to that for non-spine fracture for each drug, but differs among drugs. Based on the current data, ALN reduces the risk of hip and non-spine fracture by 49-55%, HT by 25-36% and RIS by 26-27%. There is insufficient and/or inconsistent evidence of an effect on these fractures for IBN, calcitonin and raloxifene.

Antiremodeling agents influence osteoblast activity differently in modeling and remodeling sites of canine rib

Antiremodeling agents reduce bone loss in part through direct actions on osteoclasts. Their effects on osteoblasts and bone formation activity are less clear and may differ at sites undergoing modeling vs. remodeling. Skeletally mature intact beagles, 1-2 years old at the start of the study, were treated daily with clinically relevant doses of alendronate (0.10 or 0.20 mg/kg), risedronate (0.05 or 0.10 mg/kg), raloxifene (0.50 mg/kg), or vehicle (1 mL/kg). Dynamic bone formation parameters were histologically assessed on periosteal, endocortical/trabecular, and intracortical bone envelopes of the rib. Raloxifene significantly increased periosteal surface mineral apposition rate (MAR), a measure of osteoblast activity, compared to all other treatments (+108 to +175%, P < 0.02), while having no significant effect on MAR at either the endocortical/trabecular or intracortical envelope. Alendronate (both 0.10 and 0.20 doses) and risedronate (only the 0.10 dose) significantly (P < or = 0.05) suppressed MAR on the endocortical/trabecular envelope, while none of the bisphosphonate doses significantly altered MAR at either the periosteal or intracortical envelopes compared to vehicle. Based on these results, we conclude that (1) at clinically relevant doses the two classes of antiremodeling agents, bisphosphonates and selective estrogen receptor modulators, exert differential effects on osteoblast activity in the canine rib and (2) this effect depends on whether modeling or remodeling is the predominant mechanism of bone formation.

Osteoporosis update: effective prevention and treatment

Osteoporosis is a public health threat to approximately 44 million individuals in the USA, or 55% of men and women over the age of 50 years. The primary goal of osteoporosis management is to prevent fracture, the most devastating consequence. Risk factors and bone mineral density can be assessed to determine appropriate action for prevention and treatment of osteoporosis. Prevention strategies include lifestyle modification, fall prevention, and adequate intake of calcium and vitamin D. Current treatment options include antiresorptive agents and anabolic agents. Adherence and cost issues play major roles in establishing optimal therapy for individual patients. New agents in development are designed to improve osteoporosis treatment and patient adherence. This review focuses on current and future prevention and treatment options for postmenopausal osteoporosis.

Drug insight: Bisphosphonates for postmenopausal osteoporosis

Bisphosphonates are potent antiresorptive agents, which have largely been used for the treatment of postmenopausal osteoporosis during the past 10 years. When embedded in bone matrix, bisphosphonates are taken up by osteoclasts engaged in bone resorption, leading--mainly by inhibition of farnesyl diphosphate synthase, a key enzyme of the mevalonate pathway--to osteoclast apoptosis. Bone resorption decreases, with consequent improvement in the mechanical properties of bone and a reduced risk of fracture. Alendronate and risedronate are oral nitrogen-containing bisphosphonates. Several randomized, placebo-controlled trials have shown the ability of these bisphosphonates to halve the risk of vertebral fracture when taken daily for 3 years. Nonvertebral fracture risk, including that at the hip, was also significantly decreased. Weekly regimens have simplified the administration of bisphosphonates and, probably, improved adherence to treatment. A significant reduction in the risk of vertebral fracture has also been demonstrated with an intermittent regimen of ibandronate, which is a new, potent, nitrogen-containing bisphosphonate. Ibandronate was recently marketed for use in an oral, once-monthly dose of 150 mg, with the goal of improving compliance. Bisphosphonates are usually well tolerated in the long term. Intravenous administration of bisphosphonates in women with osteoporosis, which is currently under investigation, might be an interesting future option for women who cannot tolerate oral regimens, and for enhancing compliance.

Alendronate sodium in the management of osteoporosis

Alendronate is one of the best and most extensively studied bisphosphonates in the treatment of osteoporosis. This review considers in detail the major pivotal study, the fracture intervention trial (FIT), upon which the use of alendronate is based and which was a landmark study in terms of design, size and clinical impact. The role of alendronate has subsequently been underscored by a range of studies extending the clinical indications for its use and consolidating the effect on reducing both vertebral and non-vertebral fracture risk. Although the emphasis of these studies has predominantly been on the management of postmenopausal osteoporosis, data is also available in primary prevention, men, and glucocorticoids-induced osteoporosis. Direct comparison between the different drugs used to treat osteoporosis with fracture end points are needed for patients and doctors to make informed choices, but the size of such studies are prohibitive. Clinical trials using surrogate markers such as bone mineral density and biochemical markers of bone turnover have been performed which provide some helpful information but the limitations of this approach need to be recognized.

An update on biomarkers of bone turnover and their utility in biomedical research and clinical practice

BACKGROUND

Maintenance of the structural and functional integrity of the skeleton is a critical function of a continuous remodeling driven by highly associated processes of bone resorption and synthetic activities driven by osteoclasts and osteoblasts, respectively. Acceleration of bone turnover, accompanied with a disruption of the coupling between these cellular activities, plays an established role in the pathogenesis of metabolic bone diseases, such as osteoporosis. During the past decades, major efforts have been dedicated to the development and clinical assessment of biochemical markers that can reflect the rate of bone turnover. Numerous studies have provided evidence that serum levels or urinary excretion of these biomarkers correlate with the rate of bone loss and fracture risk, proving them as useful tools for improving identification of high-risk patients.

OBJECTIVE

The aim of the present review is to give an update on biomarkers of bone turnover and give an overview of their applications in epidemiological and clinical research.

DISCUSSION

Special attention is given to their utility in clinical trials testing the efficacy of drugs for the treatment of osteoporosis and how they supplement bone mass measurements. Recent evidence suggests that biochemical markers may provide information on bone age that may have indirectly relates to bone quality; the latter is receiving increasing attention. A more targeted use of biomarkers could further optimize identification of high-risk patients, the process of drug discovery, and monitoring of the efficacy of osteoporosis treatment in clinical settings.

Prevention and treatment of osteoporosis in inflammatory bowel disease

The following are guidelines for evaluation and consideration for treatment of patients with inflammatory bone disease (IBD) after bone mineral density (BMD) measurements. The Crohn's & Colitis Foundation of America (CCFA) has indicated that its recommendations are intended to serve as reference points for clinical decision-making, not as rigid standards, limits, or rules. They should not be interpreted as quality standards.

Effects of dehydroepiandrosterone replacement therapy on bone mineral density in older adults: a randomized, controlled trial

CONTEXT

Dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) decrease with aging and are important androgen and estrogen precursors in older adults. Declines in DHEAS with aging may contribute to physiological changes that are sex hormone dependent.

OBJECTIVE

The aim was to determine whether DHEA replacement increases bone mineral density (BMD) and fat-free mass.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, double-blinded, controlled trial was conducted at an academic research institution. Participants were 70 women and 70 men, aged 60-88 yr, with low serum DHEAS levels.

INTERVENTION

The intervention was oral DHEA 50 mg/d or placebo for 12 months.

MEASUREMENTS

BMD, fat mass, and fat-free mass were measured before and after intervention.

RESULTS

Intent-to-treat analyses revealed trends for DHEA to increase BMD more than placebo at the total hip (1.0%, P = 0.05), trochanter (1.2%, P = 0.06), and shaft (1.2%, P = 0.05). In women only, DHEA increased lumbar spine BMD (2.2%, P = 0.04; sex-by-treatment interaction, P = 0.05). In secondary compliance analyses, BMD increases in hip regions were significant (1.2-1.6%; all P < 0.02) in the DHEA group. There were no significant effects of DHEA on fat or fat-free mass in intent-to-treat or compliance analyses.

CONCLUSIONS

DHEA replacement therapy for 1 yr improved hip BMD in older adults and spine BMD in older women. Because there have been few randomized, controlled trials of the effects of DHEA therapy, these findings support the need for further investigations of the benefits and risks of DHEA replacement and the mechanisms for its actions.

Effects of 3- and 5-year treatment with risedronate on bone mineralization density distribution in triple biopsies of the iliac crest in postmenopausal women

Long-term effects of risedronate on bone mineralization density distribution in triple transiliac crest biopsies of osteoporotic women were evaluated. In this double-blinded study, 3- and 5-year treatment with risedronate increased the degree and homogeneity of mineralization without producing hypermineralization. These changes at the material level of bone could contribute to risedronate's antifracture efficacy.

INTRODUCTION

Risedronate, a nitrogen-containing bisphosphonate, is widely used in the treatment of osteoporosis. It reduces bone turnover, increases BMD, and decreases fracture risk. To date, there are no data available on the long-term effects of risedronate on bone mineralization density distribution (BMDD) in humans.

MATERIALS AND METHODS

Osteoporotic women enrolled in the VERT-NA trial received either risedronate (5 mg/day, orally) or placebo for up to 5 years. All subjects received calcium and vitamin D supplementation if deficient at baseline. Triple iliac crest biopsies were collected from a subset of these subjects at baseline and 3 and 5 years. BMDD was measured in these biopsies using quantitative backscattered electron imaging, and the data were also compared with a normal reference group.

RESULTS

At baseline, both risedronate and placebo groups had a lower degree and a greater heterogeneity of mineralization as well as an increase in low mineralized bone compared with the normal reference group. The degree of mineralization increased significantly in the risedronate as well as in the placebo group after 3- and 5-year treatment compared with baseline. However, the degree of mineralization did not exceed that of normal. Three-year treatment with risedronate significantly increased the homogeneity of mineralization and slightly decreased low mineralized bone compared with placebo. Surprisingly with 5-year risedronate treatment, heterogeneity of mineralization increased compared with 3-year treatment, which might indicate an increase in newly formed bone.

CONCLUSIONS

Long-term treatment with risedronate affects the homogeneity and degree of mineralization without inducing hypermineralization of the bone matrix. These changes at the material level of the bone matrix may contribute to risedronate's antifracture efficacy in osteoporotic patients.

Osteoporosis

Osteoporosis is a serious public health issue. The past 10 years have seen great advances in our understanding of its epidemiology, pathophysiology, and treatment, and further advances are rapidly being made. Clinical assessment will probably evolve from decisions mainly being made on the basis of bone densitometry, to use of algorithms of absolute fracture risk. Biochemical markers of bone turnover are also likely to become more widely used. Bisphosphonates will probably remain the mainstay of therapy, but improved understanding of the optimum amount of remodelling suppression and duration of therapy will be important. At the same time, other diagnostic and therapeutic approaches, including biological agents, are likely to become more widespread.

Alterations in canine vertebral bone turnover, microdamage accumulation, and biomechanical properties following 1-year treatment with clinical treatment doses of risedronate or alendronate

One year of treatment with bisphosphonates at 5x the dose used for post-menopausal osteoporosis significantly increases failure load and microdamage, and decreases toughness at multiple skeletal sites in intact female beagles. The goal of this study was to determine if similar changes occur with doses equivalent to those used for post-menopausal osteoporosis treatment. Skeletally-mature female beagles were treated daily for 1 year with vehicle (VEH) or one of three doses of risedronate (RIS; 0.05, 0.10, 0.50 mg/kg/day) or alendronate (ALN; 0.10, 0.20, 1.00 mg/kg/day). Doses of ALN corresponded to treatment dose for PMO, 1/2 that dose, and 5x that dose on a mg/kg basis; RIS was given at a dose-equivalent to ALN. Vertebral density, geometry, percent ash, static/dynamic histology, microdamage, and biomechanical parameters were quantified. Trabecular bone activation frequency (Ac.f) was dose-dependently lower in RIS-treated groups (-40%, -66%, -84%, P < 0.05 vs. VEH) while the three ALN groups were all similarly lower compared to VEH (-65%, -71%, -76%; P <0.05). Crack surface density (Cr.S.Dn) was significantly higher than VEH for all doses of RIS and ALN (+2.9 to 5.4-fold vs. VEH). Stiffness was significantly increased with both agents while there were no significant changes in any other structural or estimated material properties. Cr.S.Dn and Ac.f exhibited a significant non-linear correlation (r(2) = 0.21; P < 0.001) while there was no relationship between Cr.S.Dn and any mechanical properties. These results document that 1 year of bisphosphonate treatment at clinical doses allows significant accumulation of microdamage in the vertebra but this is offset by increases in bone volume and mineralization such that there is no significant impairment of mechanical properties.

Update of current therapeutic options for the treatment of postmenopausal osteoporosis

BACKGROUND

Osteoporosis is a common chronic condition in elderly women and is associated with decreased bone strength and an increased risk for fractures. As the incidence of osteoporotic fractures continues to rise, it is important to identify the most effective therapies for reducing patients' risk of fracture.

OBJECTIVE

This article reviews the medication classes commonly used for treating osteoporosis and the efficacy, tolerability, and drug-interaction potential of specific medications. The evidence for the use of combination therapies is summarized, as are the agents under investigation.

METHODS

Relevant articles were identified through a search of MEDLINE (August 1985-August 2005) using the terms osteoporosis, postmenopausal, fracture, and efficacy combined with drug therapy, calcium, vitamin D, estrogen, progesterone, selective estrogen modulators, calcitonin, strontium ranelate, bisphosphonates, alendronate, risedronate, ibandronate, pamidronate, parathyroid hormone, combination therapy, and zoledronic acid. The identified articles were reviewed for suitability, with priority given to meta-analyses.

RESULTS

Among the therapeutic options for the treatment of osteoporosis, the bisphosphonates appear to provide the greatest antiresorptive efficacy, with some bisphosphonates providing 7% to 8% increases in bone mineral density and 60% to 70% decreases in markers of bone resorption. Bisphosphonates also may reduce the incidence of new vertebral fractures by 50% to 52%.

CONCLUSIONS

Bisphosphonates are currently the first choice for the treatment of osteoporosis. Use of intermittent regimens of the newer bisphosphonates appears to be a promising alternative to administration of daily or weekly treatment.

Mice lacking cathepsin K maintain bone remodeling but develop bone fragility despite high bone mass

Bone microstructural and biomechanical properties were analyzed in mice genetically lacking cathepsin K (CatK). CatK deficiency (CatK(-/-)) produced mild osteopetrosis, elevated numbers of osteoclasts, regions of disorganized bone microstructure, and increased bone fragility, showing how chronic alteration of enzyme activity during skeletal development dramatically affects bone organization and function.

INTRODUCTION

Mouse models of CatK deficiency recapitulate the osteopetrosis of human pyknodysostosis and allow study of clinically relevant issues: how inhibition of this enzyme activity affects bone integrity structurally and biomechanically. To address these questions, we generated CatK-deficient mice by targeted disruption of the Ctsk gene and compared their bone structural and mechanical properties with wildtype (WT) controls.

MATERIALS AND METHODS

Standard histomorphometric and biomechanical analyses were performed on femora from C57BL/6J male and female CatK(-/-), CatK(+/-), and WT mice.

RESULTS

CatK(-/-) femora exhibited the mild metaphyseal osteopetrosis, a greater cortical bone area and thickness, normal bone strength, but a high degree of brittleness (nearly 50-70% decrease in postyield displacement versus WT) and a 30-40% reduction in the work-to-failure. In cancellous bone, osteoclast numbers and resorption surface were increased markedly (approximately 150% and 50%, respectively), despite the overall decrease in net bone resorption for CatK-deficient mice. Bone formation indices were altered in CatK(-/-) mice as well, with significant increases in mineral appositional rate, but not in bone formation surface; these data suggest difference in osteoblast work but not in their recruitment in CatK deficiency. CatK-deficient cortical bones had large areas of woven bone and intracortical resorption spaces within the disorganized tissue. Bone phenotype in CatK(-/-) was similar in males and females.

CONCLUSIONS

Genetic CatK deficiency in mice results not only in the impairment of osteoclast function and osteopetrosis, but also altered osteoblast function, defective tissue organization, and very brittle bones. Whether this bone fragility in CatK deficiency results entirely from indirect effects of suppressed bone turnover because of impaired osteoclast function or perhaps represents a previously unappreciated more direct role for CatK in bone formation remains to be established.

Postmenopausal osteoporosis. What have we learned since the introduction of bisphosphonates?

Over the past 12 years bisphosphonates have become a mainstay of treatment for postmenopausal osteoporosis. As a class, bisphosphonates significantly suppress bone turnover and increase BMD at the lumbar spine and other site through their direct inhibitory effects on osteoclasts. Alendronate and risedronate reduce the incidence of clinical vertebral and non-vertebral fractures. Etidronate and both oral and intravenous ibandronate reduce the incidence of clinical vertebral fractures, but data from primary analyses for reduction in non-vertebral fractures are currently less robust. Intravenous administration of zoledronate is under late-stage investigation for use in postmenopausal osteoporosis. Combinations of alendronate with estrogen or raloxifene provide a greater reduction in bone turnover markers and greater increases in BMD, but fracture risk reduction has not been determined. Overall, bisphosphonates are well tolerated. The most common side effects of oral bisphosphonates are upper gastrointestinal symptoms. Newer safety concerns about the use of bisphosphonates include osteonecrosis of the jaw and oversuppression of bone turnover. The optimal duration of bisphosphonate treatment has not been clearly established.

Relative binding affinities of bisphosphonates for human bone and relationship to antiresorptive efficacy

Potent bisphosphonates (BPs) preferentially bind bone at sites of active osteoclastic bone resorption, where they are taken up by the osteoclast and inhibit resorption. We tested the hypothesis that BP affinity to human bone affects antiresorptive potency. [(1)(4)C]-Alendronate binding to human bone was saturable and reversible with an apparent Kd of 72 microM by Scatchard analysis. In competition binding assays, unlabeled alendronate (Ki: 61 microM) was slightly more potent than pyrophosphate (Ki = 156 microM) in blocking [(1)(4)C]-alendronate binding. Likewise, most tested BPs, including etidronate (Ki: 91 microM), ibandronate (116 microM), pamidronate (83 microM), risedronate (85 microM) and zoledronate (81 microM), showed comparable affinities. Interestingly, tiludronate (173 microM; P < 0.05 vs. all other BPs) and especially clodronate (806 microM; P > 0.0001 vs. all other BPs) displayed significantly weaker affinity for bone. The weak affinity of clodronate translated into a requirement for 10-fold higher dosing in in vitro bone resorption assays when bone was pretreated with BP and subsequently washed prior to adding osteoclasts. In stark contrast, neither alendronate nor risedronate lost any efficacy after washing the bone surface. These findings suggest that most clinically tested BPs may have similar affinities for human bone. For those with reduced affinity, this may translate into lower potency that necessitates higher dosing.

Once-monthly Ibandronate for postmenopausal Osteoporosis: Review of a new dosing regimen

BACKGROUND

Ibandronate, a nitrogen-containing bisphosphonate, was approved by the US Food and Drug Administration (FDA) in May 2003 as a daily oral regimen for the treatment and prevention of post-menopausal osteoporosis. In March 2005, the FDA approved once-monthly dosing with ibandronate for the same indications.

OBJECTIVE

The purpose of this article was to review the efficacy and tolerability of ibandronate 150 mg once monthly in the treatment and prevention of post-menopausal osteoporosis.

METHODS

A search of MEDLINE (1966-September 2005) and International Pharmaceutical Abstracts (1971-September 2005) for articles relating to the efficacy and tolerability of once-monthly ibandronate in the treatment of postmenopausal osteoporosis was conducted using the terms ibandronate and ibandronic acid. Additional searches were conducted to identify publications relevant to compliance and pharmacoeconomic considerations using the terms bispbospbonate, compliance, cost, and pharmacoeconomics. The reference lists of identified articles and presentations from recent scientific meetings also were reviewed. Selected safety information from the manufacturer was incorporated.

RESULTS

Ibandronate 2.5 mg/d and intermittent ibandronate (20 mg QOD for 12 doses every 3 months) have been shown to effectively reduce the incidence of vertebral fractures; after 3 years of therapy in a placebo-controlled clinical trial, the relative risk reductions for new vertebral fractures with daily and intermittent ibandronate were 62% and 50%, respectively (both, P<0.001 vs placebo). Once-monthly ibandronate has been evaluated in 2 clinical trials: a Phase I dose-ranging trial in 144 healthy postmenopausal women and a Phase III noninferiority trial in 1609 women with postmenopausal osteoporosis who were randomized to receive ibandronate 2.5 mg/d or 1 of 3 monthly ibandronate regimens: 50/50 mg (50 mg given on 2 consecutive days) once monthly; 100 mg once monthly; and 150 mg once monthly. The primary end point of the Phase III trial was the change from baseline in lumbar spine bone mineral density (BMD). After 1 year of therapy, patients who received ibandronate 150 mg once monthly had a significantly greater increase from baseline in lumbar spine BMD compared with those who received ibandronate 2.5 mg/d (4.9% vs 3.9%, respectively; P=0.002). The overall adverse-event profile was similar between the daily and monthly regimens. Drug-related adverse events were reported in 32.4% of patients receiving ibandronate 2.5 mg/d and 36.9% of patients receiving ibandronate 150 mg monthly. Upper gastrointestinal adverse events occurred in a respective 22.8% and 22.5% of the 2 groups. After 1 year of therapy, patients receiving ibandronate 150 mg monthly reported more flulike symptoms (8.3%) compared with those receiving ibandronate 2.5 mg/d (2.8%). In a crossover study comparing preference for and convenience of monthly ibandronate and weekly alendronate in 342 ambulatory women with postmenopausal osteoporosis, significantly more patients preferred the monthly ibandronate regimen to the weekly alendronate regimen (71.4% vs 28.5%, respectively; P<0.001).

CONCLUSION

Once-monthly ibandronate is an effective and well-tolerated treatment option for postmenopausal osteoporosis.

Monitoring osteoporosis therapy: bone mineral density, bone turnover markers, or both?

Monitoring the efficacy associated with antiresorptive therapy is an intuitive yet integral part of successful osteoporosis management. Although response rates to bisphosphonates in clinical trials--as judged by changes in bone mineral density (BMD)--are generally high, a small percentage of compliant patients do not respond. Accordingly, monitoring may help identify noncompliant patients and allow for other, possibly more successful, therapeutic interventions. Dual energy x-ray absorptiometry is the accepted method of assessing BMD to determine the need for treatment and to monitor its effects. Change in BMD is considered a valid intermediate end point for efficacy of fracture risk reduction. However, clinical trials have shown that the reduction in fracture risk associated with antiresorptive therapy may occur before changes in BMD become apparent. Vertebral fracture benefit is observed even among women who maintain rather than gain BMD during antiresorptive therapy. Clinical trials show that suppression of bone turnover markers after as little as 3 months of therapy is strongly associated with reductions in risk for fracture. Although formal guidelines for monitoring bone turnover markers do not yet exist, there are data to suggest that changes in these markers are valid intermediate endpoints for efficacy of fracture risk reduction that may provide valuable additional data on therapeutic success, particularly early in treatment and before changes in BMD become apparent.

Oral ibandronate in the management of postmenopausal osteoporosis: Review of upper gastrointestinal safety

Oral daily bisphosphonates carry a potential for gastrointestinal (GI) adverse events, which has been partly addressed by introducing once-weekly regimens. Nevertheless, the need to follow inconvenient dosing instructions every week could still hinder long-term compliance and therapeutic outcome. In addition, survey data indicates that many patients would prefer a once-monthly rather than once-weekly bisphosphonate dosing regimen. Ibandronate is a potent, nitrogen-containing bisphosphonate specifically developed for less frequent administration. In a pivotal study in postmenopausal osteoporosis, oral ibandronate, administered daily or with a between-dose interval of >2 months, demonstrated robust antifracture efficacy and an overall incidence of upper GI adverse events similar to placebo, even in patients at increased risk of such events. This and other clinical studies conducted in postmenopausal women demonstrate that oral ibandronate has an excellent upper GI safety profile.

Risedronate for prevention and treatment of osteoporosis in postmenopausal women

Risedronate sodium is an N-containing bisphosphonate that has been approved for the prevention and treatment of osteoporosis in postmenopausal women. An increase in the rate of bone remodelling is a regular feature of oestrogen withdrawal during the menopausal transition, but excessive remodelling leads to bone fragility. Risedronate and similar compounds reduce the rate of bone remodelling by suppressing the action of osteoclasts. The antifracture efficacy of risedronate is impressive. In large clinical trials of postmenopausal women with osteoporosis-related fracture(s) at entry, the risk of incident vertebral and non-vertebral fractures was reduced by approximately 40%. In older women at risk for hip fracture, incident hip fractures were also reduced by approximately 40%. Antifracture efficacy develops within the first 6 months, and treatment has been followed for as long as 5 years without deleterious effects on bone. We await reports of experience with risedronate in 'real-world' cases of greater complexity (i.e., in patients with co-morbidities and medications that would have excluded them from published clinical trials).