The inhibition of human farnesyl pyrophosphate synthase by nitrogen-containing bisphosphonates. Elucidating the role of active site threonine 201 and tyrosine 204 residues using enzyme mutants

Farnesyl pyrophosphate synthase (FPPS) is the major molecular target of nitrogen-containing bisphosphonates (N-BPs), used clinically as bone resorption inhibitors. We investigated the role of threonine 201 (Thr201) and tyrosine 204 (Tyr204) residues in substrate binding, catalysis and inhibition by N-BPs, employing kinetic and crystallographic studies of mutated FPPS proteins.Mutants of Thr201 illustrated the importance of the methyl group in aiding the formation of the Isopentenyl pyrophosphate (IPP) binding site, while Tyr204 mutations revealed the unknown role of this residue in both catalysis and IPP binding. The interaction between Thr201 and the side chain nitrogen of N-BP was shown to be important for tight binding inhibition by zoledronate (ZOL) and risedronate (RIS), although RIS was also still capable of interacting with the main-chain carbonyl of Lys200. The interaction of RIS with the phenyl ring of Tyr204 proved essential for the maintenance of the isomerized enzyme-inhibitor complex. Studies with conformationally restricted analogues of RIS reaffirmed the importance of Thr201 in the formation of hydrogen bonds with N-BPs.In conclusion we have identified new features of FPPS inhibition by N-BPs and revealed unknown roles of the active site residues in catalysis and substrate binding.     

Zoledronic acid enhances bone-implant osseointegration more than alendronate and strontium ranelate in ovariectomized rats

Summary

This study was designed to compare the effects of alendronate (ALN), strontium ranelate (SR), and zoledronic acid (ZOL) on bone-implant osseointegration in ovariectomized rats. Histological examination and biomechanical tests show that ZOL, ALN, and SR enhance bone-implant osseointegration; ALN and SR have similar effects, while ZOL enhances bone-implant osseointegration more than ALN and SR

Introduction

This study aims to compare the effects of ALN, SR, and ZOL on bone-implant osseointegration in ovariectomized rats.

Methods

Sixty female Sprague–Dawley rats were included in this study. Of them, 48 rats were ovariectomized (OVX) and assigned to four groups: OVX (OVX?+?Veh), ALN (OVX?+?ALN), SR (OVX?+?SR), and ZOL (OVX?+?ZOL). And another 12 rats were sham-operated as a control group (Sham). Four weeks after ovariectomy, HA-coated titanium implants were inserted into the tibias bilaterally in all rats. Then the rats in groups ALN, SR, and ZOL were systemically administrated with alendronate (7 mg/kg/week, orally), strontium ranelate (500 mg/kg/day, orally), or a single injection of zoledronic acid (0.1 mg/kg, iv), respectively. Twelve weeks after implantation, all rats were sacrificed to get the femurs and tibias. Histological examination and biomechanical tests were used to evaluate bone-implant osseointegration in all groups.

Results

ALN, SR, and ZOL significantly increased distal femoral BMD when compared with group OVX; ZOL increased BMD significantly more than ALN and SR (P?<?0.05). Significant increase of bone-to-implant contact and peri-implant bone fraction were observed in groups ALN, SR, and ZOL when compared with group OVX (P?<?0.05). Groups ALN and SR were inferior to groups ZOL and Sham (P?<?0.05) in bone-to-implant contact and peri-implant bone fraction. Similar results were found in biomechanical testing (max pushout force).

Conclusions

In rats losing bone rapidly after ovariectomy, systemic administration of ZOL, ALN, and SR causes better bone-implant osseointegration when compared to OVX; ALN and SR have similar positive effects on osseointegration, while ZOL, that was given in a dose with more positive BMD effect than that of ALN or SR, causes better osseointegration than either ALN or SR.     

The level of ATP analog and isopentenyl pyrophosphate correlates with zoledronic acid-induced apoptosis in cancer cells in vitro

Bisphosphonates are potent inhibitors of osteoclast function widely used to treat excessive bone resorption associated, e.g., with bone metastases. They have also antitumor activity. However, it is unclear whether this reflects an indirect effect via inhibition of bone resorption or a direct antitumor effect.Nitrogen-containing bisphosphonates (N-BPs), including zoledronic acid (ZOL), act by inhibiting farnesyl pyrophosphate synthase (FPPS). The mevalonate pathway is blocked and the accumulation of isopentenyl pyrophosphate (IPP) consequently occurs. IPP is conjugated to AMP to form a novel ATP analog (ApppI). The present study was undertaken to clarify whether IPP and/or ApppI has a direct involvement in apoptosis caused by ZOL in different cancer cell lines.There are marked differences in ZOL-induced ApppI formation between different cancer cell lines. On this basis, we selected three cancer cell lines that differ significantly from each other in their ZOL-induced IPP and ApppI accumulation: human estrogen-dependent (MCF7) and estrogen-independent (MDA-MB 436) breast cancer cell lines and a human myeloma cell line (RPMI 8226).The amount of IPP/ApppI correlated with the capacity of cells to undergo apoptosis. Geranylgeraniol (GGOH), an intermediate of mevalonate metabolism, blocks both IPP and ApppI formation and to some degree ZOL-induced apoptosis in a cell line-dependent manner. In addition, lovastatin (LOV), an inhibitor of the enzyme HMGCoA reductase, completely blocks IPP/ApppI formation as determined by mass spectrometry analysis, but enhances apoptosis.In conclusion, the current data suggest that ZOL-induced IPP/ApppI formation can contribute to ZOL-induced apoptosis. This mechanism and the inhibition of protein prenylation, both outcomes of FPPS inhibition in mevalonate pathway, seem to act in concert in ZOL-induced apoptosis in cancer cells.     

Nitrogen-containing bisphosphonates can inhibit angiogenesis in vivo without the involvement of farnesyl pyrophosphate synthase

Nitrogen-containing bisphosphonates (N-BPs) are widely used to block bone destruction associated with bone metastasis because they are effective inhibitors of osteoclast-mediated bone resorption. More specifically, once internalized by osteoclasts, N-BPs block the activity of farnesyl pyrophosphate synthase (FPPS), a key enzyme in the mevalonate pathway. In addition to their antiresorptive activity, preclinical evidence shows that N-BPs have antiangiogenic properties. However, the exact reasons for which N-BPs inhibit angiogenesis remain largely unknown. Using different angiogenesis models, we examined here the effects of zoledronate, risedronate and three structural analogs of risedronate (NE-58025, NE-58051 and NE-10790) with lower potencies to inhibit FPPS activity. Risedronate and zoledronate were much more potent than NE-compounds at inhibiting both endothelial cell proliferation in vitro and vessel sprouting in the chicken egg chorioallantoic membrane (CAM) assay. In addition, only risedronate and zoledronate inhibited the revascularization of the prostate gland in testosterone-stimulated castrated rats. Moreover, as opposed to NE-compounds, risedronate and zoledronate induced intracellular accumulation of isopentenyl pyrophosphate (IPP) in endothelial cells by blocking the activity of the IPP-consuming enzyme FPPS. Thus, these results indicated that N-BPs inhibited angiogenesis in a FPPS-dependent manner. However, drug concentrations used to inhibit angiogenesis, both in vitro and in the CAM and prostate gland assays, were high. In contrast, a low concentration of risedronate (1 μM) was sufficient to inhibit blood vessel formation in the ex vivo rat aortic ring assay. Moreover, NE-58025 (which had a 7-fold lower potency than risedronate to inhibit FPPS activity) was as effective as risedronate to reduce angiogenesis in the rat aortic ring assay. In conclusion, our results suggest that low concentrations of N-BPs inhibit angiogenesis in a FPPS-independent manner, whereas higher drug concentrations were required to inhibit FPPS activity in vivo.     

The Pharmacological Profile of a Novel Highly Potent Bisphosphonate,OX14 (1‐Fluoro‐2‐(Imidazo‐[1,2‐α]Pyridin‐3‐yl)‐Ethyl‐Bisphosphonate)

Bisphosphonates are widely used in the treatment of clinical disorders characterized by increased bone resorption, including osteoporosis, Paget's disease, and the skeletal complications of malignancy. The antiresorptive potency of the nitrogen‐containing bisphosphonates on bone in vivo is now recognized to depend upon two key properties, namely mineral binding affinity and inhibitory activity on farnesyl pyrophosphate synthase (FPPS), and these properties vary independently of each other in individual bisphosphonates. The better understanding of structure activity relationships among the bisphosphonates has enabled us to design a series of novel bisphosphonates with a range of mineral binding properties and antiresorptive potencies. Among these is a highly potent bisphosphonate, 1‐fluoro‐2‐(imidazo‐[1,2 alpha]pyridin‐3‐yl)‐ethyl‐bisphosphonate, also known as OX14, which is a strong inhibitor of FPPS, but has lower binding affinity for bone mineral than most of the commonly studied bisphosphonates. The aim of this work was to characterize OX14 pharmacologically in relation to several of the bisphosphonates currently used clinically. When OX14 was compared to zoledronate (ZOL), risedronate (RIS), and minodronate (MIN), it was as potent at inhibiting FPPS in vitro but had significantly lower binding affinity to hydroxyapatite (HAP) columns than ALN, ZOL, RIS, and MIN. When injected i.v. into growing Sprague Dawley rats, OX14 was excreted into the urine to a greater extent than the other bisphosphonates, indicating reduced short‐term skeletal uptake and retention. In studies in both Sprague Dawley rats and C57BL/6J mice, OX14 inhibited bone resorption, with an antiresorptive potency equivalent to or greater than the comparator bisphosphonates. In the JJN3‐NSG murine model of myeloma‐induced bone disease, OX14 significantly prevented the formation of osteolytic lesions (p < 0.05). In summary, OX14 is a new, highly potent bisphosphonate with lower bone binding affinity than other clinically relevant bisphosphonates. This renders OX14 an interesting potential candidate for further development for its potential skeletal and nonskeletal benefits. © 2017 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc.     

Serum homocysteine, folate and vitamin B12 in patients with Paget’s disease of bone: the effect of zoledronic acid

High serum homocysteine (HCY) and indirectly deficiency of folate and/or vitamin B₁₂ stimulate bone resorption and adversely affect collagen cross-linking. The aim of this study was the evaluation of serum levels of HCY, folate and vitamin B₁₂ in patients with Paget’s disease of bone (PDB) and the effect of zoledronic acid (ZOL) on their serum levels. Nine consecutive patients with polyostotic PDB (median age 66 years) received a single 5-mg ZOL infusion. Blood samples for HCY, folate, vitamin B₁₂, 25-hydroxyvitamin D (25-OH-D), total serum alkaline phosphatase (TSAP), bone-specific serum alkaline phosphatase (BSAP) and C-terminal cross-linking telopeptide of type I collagen (CTX) were obtained at baseline and 3, 6 and 12 months after ZOL infusion. Twelve age-, gender- and BMI-matched healthy individuals were recruited for the control group at baseline assessment. Patients with PDB had significantly higher serum HCY (p = 0.028), folate (p < 0.001) and bone markers [TSAP (p < 0.001), BSAP (p < 0.001) and CTX (p < 0.001)] compared with the control group at baseline. In the pagetic group, serum HCY significantly decreased 3 months after ZOL infusion and remained essentially unchanged up to the end of the study (p = 0.005). Serum vitamin B₁₂ and folate remained unaffected throughout the study. Our data suggest that serum HCY levels are increased in patients with PDB. A single ZOL infusion results in a decrease in HCY levels that might represent another mechanism for the reduction of the activity of PDB achieved by ZOL.     

Differentiating the mechanisms of antiresorptive action of nitrogen containing bisphosphonates

Bisphosphonates (BPS) inhibit bone resorption and are divided into two classes according to their chemical structure and mechanism of action: nonnitrogen containing BPS such as etidronate and clodronate that are of low potency and inhibit osteoclast function via metabolism into toxic ATP-metabolites and nitrogen-containing BPS (NBPS), such as alendronate and risedronate that inhibit the enzyme of the mevalonate biosynthetic pathway farnesyl pyrophosphate synthase (FPPS), resulting in inhibition of the prenylation of small GTP-binding proteins in osteoclasts and disruption of their cytoskeleton. Previously, studies in various cell types suggested, however, that pamidronate functions by mechanism(s) additional or independent of the mevalonate pathway. To examine if such mechanism(s) are also involved in the action of NBPS on osteoclastic bone resorption, we examined the action of alkyl and heterocyclic NBPS with close structural homology on FPPS/isopentenyl pyrophosphate isomerase (IPPI) activity, on osteoclastic resorption, and on reversibility of this effect with GGOH. As expected, both pamidronate and alendronate suppressed bone resorption and FPPS/IPPI activity, the latter with greater potency than the first. Surprisingly, however, unlike alendronate, the antiresorptive effect of pamidronate was only partially reversible with GGOH, indicating the involvement of mechanism(s) of action additional to that of suppression of FPPS. Comparable results were obtained with the heterocyclic NBP NE-21650, a structural analog of risedronate. Thus, despite an effect on FPPS, the actions on bone resorption of some NBPS may involve mechanisms additional to suppression of FPPS. These findings may lead to identification of additional pathways that are important for bone resorption and may help to differentiate among members of the NBP class which are currently distinguished only according to their potency to inhibit bone resorption.     

Altered expression of farnesyl pyrophosphate synthase in prostate cancer: evidence for a role of the mevalonate pathway in disease progression?

Background

Preclinical studies demonstrated effects of drugs inhibiting the mevalonate pathway including nitrogen-containing bisphosphonates (N-BPs) and statins on tumor growth and progression. The exact role of this pathway in prostate cancer (PC) has not been identified yet. Herein, we evaluate the expression of farnesyl pyrophosphate synthase (FPPS), the key enzyme of the mevalonate pathway, in PC.

Patients and methods

Prostate cancer (PC) and benign prostate tissue of 114 men who underwent radical prostatectomy were constructed to a tissue microarray. Immunohistochemical staining of FPPS was quantified by the Remmele/Stegner immunoreactivity-score. Patients’ clinical follow-up was assessed. IRS was correlated to pathological and clinical data. The impact of FPPS expression on clinical course was assessed univariate and multivariate.

Results

Mean IRS in PC and benign tissue was 5.7 (95% CI 5.0–6.5) and 2.6 (2.1–3.0, p < 0.0001). Mean IRS in PC tissue of patients with organ-confined and locally advanced disease (pT ≥ 3) was 5.09 (4.22–5.96) and 6.87 (5.57–8.17, p = 0.035). IRS of PC tissue significantly correlated with Gleason score (p = 0.03). Patients with PC tissue IRS >3 showed shorter recurrence-free survival compared to the remaining (p = 0.01). Increased FPPS expression is an independent risk factor for early biochemical recurrence (p = 0.032).

Conclusions

This is the first study on FPPS in PC specimens. The association of FPPS with established histopathological risk parameters and biochemical recurrence implicates a contribution of the mevalonate pathway to PC progression. Further functional analysis is required to explore the role of this pathway in PC and to investigate whether FPPS expression affects the response of PC cells to N-BPs.     

Long-Term Effects of Amino-Bisphosphonates on Circulating γδ T Cells

The aim of this study was to explore whether desensitization to the occurrence of the acute-phase response (APR) in patients previously treated with amino-bisphosphonates (N-BPs) is due to a long-lasting reduction in the number of circulating γδ T cells. Circulating lymphocyte subpopulation counts were obtained from 63 patients with postmenopausal or senile osteoporosis at baseline and after 2?days and 12?months of the first intravenous (IV) 5?mg zoledronic acid (ZOL) infusion. At baseline both the proportion and absolute number of circulating γδ T cells were significantly higher in patients who had never used N-BPs vs. previous users, either oral or IV. A typical APR was observed in none of the patients given IV ZOL a year earlier, in 6 (22?%) of the patients previously treated with oral N-BPs, and in 13 (57?%) of the patients naive to any N-BP treatment. In patients naive to N-BPs, a significant reduction in both total lymphocytes and their subsets was observed 2?days after ZOL infusion; all these changes returned to baseline values 1?year later with the exception of γδ T cells, which remained significantly lower in terms of both proportion and absolute number. These results indicate for the first time that both IV and oral N-BP treatments are associated with a long-lasting decrease in circulating γδ T cells, and this may explain the lower incidence of APR in patients previously exposed to N-BPs. Other clinical implications of this sustained effect of N-BPs on immune-regulatory cells might be important.     

Efficacy and safety of a once‐yearly i.v. Infusion of zoledronic acid 5 mg versus a once‐weekly 70‐mg oral alendronate in the treatment of male osteoporosis: A randomized,multicenter, double‐blind,active‐controlled study

Zoledronic acid (ZOL) has shown beneficial effects on bone turnover and bone mineral density (BMD) in postmenopausal osteoporosis. This study compared the efficacy and safety of a once‐yearly i.v. infusion of ZOL with weekly oral alendronate (ALN) in men with osteoporosis. In this multicenter, double‐blind, active‐controlled, parallel‐group study, participants (n = 302) were randomized to receive either once‐yearly ZOL 5 mg i.v. or weekly oral ALN 70 mg for 24 months. Changes in BMD and bone marker levels were assessed. ZOL increased BMD at the lumbar spine, total hip, femoral neck, and trochanter and was not inferior to ALN at 24 months [least squares mean estimates of the percentage increases in lumbar spine BMD of 6.1% and 6.2%; difference approximately 0.13; 95% confidence interval (CI) 1.12–0.85 in the ZOL and ALN groups, respectively]. At month 12, the median change from baseline of markers for bone resorption [serum β‐C‐terminal telopeptide of type I collagen (β‐CTx) and urine N‐terminal telopeptide of type I collagen (NTx)] and formation [serum N‐terminal propeptide of type I collagen (P1NP) and serum bone‐specific alkaline phosphatase (BSAP)] were comparable between ZOL and ALN groups. Most men preferred i.v. ZOL over oral ALN. The incidence of adverse events and serious adverse events was similar in the treatment groups. It is concluded that a once‐yearly i.v. infusion of ZOL 5 mg increased bone density and decreased bone turnover markers similarly to once‐weekly oral ALN 70 mg in men with low bone density. © 2010 American Society for Bone and Mineral Research.     

Comparable Effects of Alendronate and Strontium Ranelate on Femur in Ovariectomized Rats

This study compared the effects of alendronate (ALN) and strontium ranelate (SR) on bone mineral density (BMD), bone histomorphometry, and biomechanics in ovariectomized (OVX) rats. We randomly assigned 48 3-month-old female Sprague–Dawley rats to four groups: sham, OVX, ALN, and SR. Rats in the OVX, ALN, and SR groups received bilateral OVX. Rats in the ALN and SR groups were orally administrated ALN (7 mg/kg/week) and SR (500 mg/kg/day). Rats in the sham and OVX groups were treated with saline. All treatments continued for 12 weeks. Femoral BMD examination, distal femoral bone histomorphometry analysis, and biomechanical tests at the femoral diaphysis and metaphysis were performed to evaluate the effects of treatments in OVX rats. Results showed that both ALN and SR significantly increased femoral BMD (total femur, diaphyseal BMD, and distal metaphyseal BMD), distal femoral bone histomorphometric parameters (BV/TV, Tb.N, and Tb.Th), and femoral biomechanical parameters (maximum load, failure load, stiffness) compared with the OVX group (P < 0.05). No differences were found between ALN and SR in increasing femoral BMD, distal femoral bone histomorphometric parameters (BV/TV, Tb.N, and Tb.Th), and femoral diaphysis biomechanical parameters (maximum load, failure load, stiffness) (P > 0.05). The SR group was inferior to the ALN group in femoral metaphysis biomechanical parameters (P < 0.05). In conclusion, ALN (7 mg/kg/week) and SR (500 mg/kg/day) have similar effects by increasing BMD, distal femoral bone histomorphometric parameters, and femoral metaphysis biomechanical properties. Although ALN has greater effects than SR on distal femoral metaphysis biomechanical properties, in general, ALN and SR have comparable effects on the femur in OVX rats.     

Effects of zoledronic acid on bone mineral density in premenopausal women receiving neoadjuvant or adjuvant therapies for HR+ breast cancer: the ProBONE II study

Summary

The effects of bisphosphonates on altered bone turnover marker (BTM) levels associated with adjuvant endocrine or chemotherapy in early breast cancer have not been systematically investigated. In ProBONE II, zoledronic acid decreased these elevated BTM levels and increased bone mineral density (BMD) during adjuvant therapy, consistent with its antiresorptive effects.

Introduction

Adjuvant chemotherapy or endocrine therapy for early hormone receptor-positive breast cancer (HR⁺ BC) is associated with rapid BMD loss and altered BTM levels. Adjuvant bisphosphonate studies demonstrated BMD increases, but did not investigate BTM effects. The randomized, double-blind, ProBONE II study investigated the effect of adjuvant zoledronic acid (ZOL) on BMD and BTM in premenopausal women with early HR⁺ BC.

Methods

Seventy premenopausal women with early HR⁺ BC received adjuvant chemotherapy and/or endocrine therapy plus ZOL (4 mg IV every 3 months) or placebo for 24 months. Primary endpoint was change in lumbar spine BMD at 24 months versus baseline. Secondary endpoints included femoral neck and total femoral BMD changes, changes in BTM, and safety.

Results

Lumbar spine BMD increased 3.14 % from baseline to 24 months in ZOL-treated participants versus a 6.43 % decrease in placebo-treated participants (P?<?0.0001). Mean changes in T- and Z-scores, and femoral neck and total femoral BMD, showed similar results. Bone resorption marker levels decreased ～55 % in ZOL-treated participants versus increases up to 65 % in placebo-treated participants (P?<?0.0001 for between-group differences). Bone formation marker (procollagen I N-terminal propeptide) levels decreased ～57 % in ZOL-treated participants versus increases up to 45 % in placebo-treated participants (P?<?0.0001 for between-group differences). Adverse events were consistent with the established ZOL safety profile and included one case of osteonecrosis of the jaw after a tooth extraction.

Conclusions

Adding ZOL to adjuvant therapy improved BMD, reduced BTM levels, and was well tolerated in premenopausal women with early HR⁺ BC receiving adjuvant chemotherapy and/or endocrine therapy.     

Cathepsin K inhibitors prevent bone loss in estrogen‐deficient rabbits

Two cathepsin K inhibitors (CatKIs) were compared with alendronate (ALN) for their effects on bone resorption and formation in ovariectomized (OVX) rabbits. The OVX model was validated by demonstrating significant loss (9.8% to 12.8%) in lumbar vertebral bone mineral density (LV BMD) in rabbits at 13‐weeks after surgery, which was prevented by estrogen or ALN. A potent CatKI, L‐006235 (L‐235), dosed at 10 mg/kg per day for 27 weeks, significantly decreased LV BMD loss (p < .01) versus OVX‐vehicle control. ALN reduced spine cancellous mineralizing surface by 70%, whereas L‐235 had no effect. Similarly, endocortical bone‐formation rate and the number of double‐labeled Haversian canals in the femoral diaphysis were not affected by L‐235. To confirm the sparing effects of CatKI on bone formation, odanacatib (ODN) was dosed in food to achieve steady‐state exposures of 4 or 9 µM/day in OVX rabbits for 27 weeks. ODN at both doses prevented LV BMD loss (p < .05 and p < .001, respectively) versus OVX‐vehicle control to levels comparable with sham or ALN. ODN also dose‐dependently increased BMD at the proximal femur, femoral neck, and trochanter. Similar to L‐235, ODN did not reduce bone formation at any bone sites studied. The positive and highly correlative relationship of peak load to bone mineral content in the central femur and spine suggested that ODN treatment preserved normal biomechanical properties of relevant skeletal sites. Although CatKIs had similar efficacy to ALN in preventing bone loss in adult OVX rabbits, this novel class of antiresorptives differs from ALN by sparing bone formation, potentially via uncoupling bone formation from resorption. © 2011 American Society for Bone and Mineral Research.     

Inhibition of bone resorption, rather than direct cytotoxicity, mediates the anti-tumour actions of ibandronate and osteoprotegerin in a murine model of breast cancer bone metastasis

Inhibition of bone resorption either by bisphosphonate (BP) treatment or by blocking RANKL signalling with osteoprotegerin (OPG) has been shown to reduce tumour burden in bone and inhibit bone destruction in murine xenograft models of breast cancer. However, whether the anti-tumour effect of OPG or BP in bone is mediated by inhibition of bone resorption or by direct effects on tumour cells is uncertain. The current study is designed to investigate anti-tumour effects of OPG and ibandronate (IBN), dosed alone or in combination, on tumour growth to determine if there is experimental support for combination treatments and to provide evidence for the presence of direct anti-tumour effects. To this aim, 10 microl (5 x 10(6) cells/ml) of the bone-seeking MDA-MB-231 (Tx-SA) cell line was injected intra-tibially into nude mice. After 10 days, when the tumours were evident radiologically, mice were treated with vehicle, OPG (1 mg/kg/day), ibandronate (IBN) (160 microg/kg/day) or IBN and OPG at the same doses (IBN+OPG) for a week, and the effects of each treatment on lytic lesions, tumour cell growth, cell apoptosis and proliferation were measured by radiography, immunohistochemistry and histomorphometry. Compared to vehicle controls, in vivo treatment with OPG, IBN, or IBN+OPG, each prevented the expansion of osteolytic bone lesions (increase in lytic lesion area day 10 to day 17: OPG -3.2%, IBN 6.6%, IBN+OPG 3.6%, Vehicle 232.5%; p<0.01). Treatment with OPG, IBN or IBN+OPG each produced similar reductions in tumour area relative to vehicle-treated mice (OPG 52%, IBN 54%, IBNp and OPG 48%, p<0.01 vs. vehicle) OPG and IBN alone and in combination each produced a similar increase in cancer cell apoptosis (OPG 330%, IBN 342%, IBN and OPG 347%, p<0.01 vs. vehicle) and a decrease in cancer cell proliferation (OPG 59%, IBN 62%, IBN and OPG 58%, p<0.05 vs. vehicle). Our findings indicate that (i) combined treatment with OPG and a bisphosphonate is not significantly more effective than either agent alone; and that (ii) inhibition of bone resorption, rather than direct anti-tumour action, mediates the effects of these agents on tumour growth in this in vivo model.     

Comparative effects of teriparatide and ibandronate on spine bone mineral density (BMD) and microarchitecture (TBS) in postmenopausal women with osteoporosis: a 2-year open-label study

Summary

Treatment effects over 2 years of teriparatide vs. ibandronate in postmenopausal women with osteoporosis were compared using lumbar spine bone mineral density (BMD) and trabecular bone score (TBS). Teriparatide induced larger increases in BMD and TBS compared to ibandronate, suggesting a more pronounced effect on bone microarchitecture of the bone anabolic drug.

Introduction

The trabecular bone score (TBS) is an index of bone microarchitecture, independent of bone mineral density (BMD), calculated from anteroposterior spine dual X-ray absorptiometry (DXA) scans. The potential role of TBS for monitoring treatment response with bone-active substances is not established. The aim of this study was to compare the effects of recombinant human 1–34 parathyroid hormone (teriparatide) and the bisphosphonate ibandronate (IBN), on lumbar spine (LS) BMD and TBS in postmenopausal women with osteoporosis.

Methods

Two patient groups with matched age, body mass index (BMI), and baseline LS BMD, treated with either daily subcutaneous teriparatide (N?=?65) or quarterly intravenous IBN (N?=?122) during 2 years and with available LS BMD measurements at baseline and 2 years after treatment initiation were compared.

Results

Baseline characteristics (overall mean ± SD) were similar between groups in terms of age 67.9?±?7.4 years, body mass index 23.8?±?3.8 kg/m², BMD L1–L4 0.741?±?0.100 g/cm², and TBS 1.208?±?0.100. Over 24 months, teriparatide induced a significantly larger increase in LS BMD and TBS than IBN (+7.6 %?±?6.3 vs. +2.9 %?±?3.3 and +4.3 %?±?6.6 vs. +0.3 %?±?4.1, respectively; P?<?0.0001 for both). LS BMD and TBS were only weakly correlated at baseline (r ²?=?0.04) with no correlation between the changes in BMD and TBS over 24 months.

Conclusions

In postmenopausal women with osteoporosis, a 2-year treatment with teriparatide led to a significantly larger increase in LS BMD and TBS than IBN, suggesting that teriparatide had more pronounced effects on bone microarchitecture than IBN.     

Preclinical pharmacology of alendronate

This brief review summarizes some of the preclinical findings of studies aimed at assessing the efficacy and safety of the aminobisphosphonate alendronate (ALN) in preventing or restoring the bone loss caused by calcium or estrogen deficiency. Mode of action studies show that ALN localizes at sites of bone resorption and inhibits osteoclastic activity. In secondary hyperparathyroidism caused by calcium-deficient diets in the rat, ALN reduced the bone loss. For low doses, daily administration proved most efficient. In ovariectomized rats, ALN both prevented and reversed the bone changes produced by estrogen deficiency at oral doses equivalent to 0.1 mg/kg per day or higher, and also maintained the mechanical strength of vertebrae. In ovariectomized baboons, which show bone changes similar to those seen in ovariectomized women, ALN also prevented the increase in bone turnover and increased both bone volume and bone strength in vertebrae. In a comparative study between ALN and etidronate, we found that ALN was 1000-fold more potent in inhibiting bone resorption and had at least a 1000-fold higher safety margin with respect to inhibition of mineralization and osteomalacia.     

Cancer treatment dosing regimens of zoledronic acid result in near‐complete suppression of mandible intracortical bone remodeling in beagle dogs

Bisphosphonate doses used in cancer treatment are substantially higher than those used for osteoporosis. Little is known about the effects of these high doses on tissue‐level remodeling suppression. The aim of this study was to assess the effects of cancer dosing regimens of zoledronic acid on tissue‐level bone remodeling at different skeletal sites. Skeletally mature female beagle dogs were treated with monthly intravenous infusions of vehicle (VEH, saline) or zoledronic acid (ZOL, 0.067 mg/kg); an additional group of animals was treated daily with oral alendronate (ALN, 0.2 mg/kg/day). Doses of ZOL and ALN were, on a milligram per kilogram basis, consistent with those used for cancer and osteoporosis, respectively. Following either 3 or 6 months of treatment, animals were euthanized, and mandible, rib, and tibia were processed for dynamic bone histology. There was no evidence of oral lesions or bone matrix necrosis in the mandibles of any animals. After 3 months, the rate of intracortical bone remodeling in the mandible was significantly suppressed with ZOL (?95%) compared with VEH; by 6 months, ZOL had produced nearly complete suppression (?99%) compared with VEH. ZOL also significantly suppressed remodeling in the rib cortex at both 3 (?83%) and 6 (?85%) months compared with VEH; tibia cortex bone formation rate was nonsignificantly lower with ZOL treatment (?68% to ?75%). Remodeling suppression in ZOL‐treated animals was significantly greater than in ALN‐treated animals at both the mandible and the rib; ALN and VEH were not different for any of the assessed parameters at any of the sites. Compared across skeletal sites, the absolute level of remodeling suppression with ZOL treatment was significantly greater at sites with higher remodeling, whereas the percent reduction was similar among the sites. These results document nearly complete intracortical remodeling suppression resulting from monthly intravenous zoledronic acid dosing, with changes being most dramatic at the mandible. Copyright © 2010 American Society for Bone and Mineral Research     

Acute Phase Response After Zoledronic Acid is Associated with Long-Term Effects on White Blood Cells

We have recently reported a long-lasting decrease in circulating γδ T cells in osteoporotic patients on oral amino-bisphosphonates (N-BPs). Here we verify whether these changes are associated with the occurrence of acute phase response (APR) to intravenous (IV) zoledronic acid (ZOL) or changes of other circulating white blood cells (WBC). WBC count was obtained before and 1 year after a single IV administration of 5 mg ZOL in 36 osteoporotic patients (mean age 72 ± 9, range 45–86 years) without other relevant diseases; 12 of 36 patients developed the classical APR. After 1 year in the patients who experienced an APR, but not in the others, a significant decrease not only of γδ T cells (?30 %), but also of total lymphocytes (?11 %) and eosinophils (?27 %), was observed. The mechanism leading to the observed decrease of circulating lymphocytes and eosinophils remains unclear, but our observation opens a new frontier for the understanding of the immunoeffects of N-BPs.     

Selection Criteria for Postmastectomy Radiotherapy in T1–T2 Tumors with 1 to 3 Positive Lymph Nodes

Background

Postmastectomy radiotherapy (PMRT) is well established in patients with ≥4 positive axillary lymph nodes (ALN); indications in 1 to 3 positive ALN remains controversial. We examined clinicopathologic criteria used for PMRT selection and compared locoregional recurrence (LRR), recurrence-free survival (RFS), and overall survival (OS) among patients with and without PMRT.

Methods

Between 1995 and 2006, a total of 1,331 patients with T1–T2 tumors and 1 to 3 positive ALN underwent mastectomy. We excluded T3/T4 tumors and neoadjuvant chemotherapy; we analyzed 1,087 patients (924 without PMRT, 163 with PMRT). Chi square testing compared clinicopathologic features between groups. The Kaplan–Meier method and Cox regression analysis examined the association between PMRT and LRR, RFS, and OS.

Results

PMRT patients were more likely to be ≤50 years old (p = 0.001) and to have larger tumors (p = 0.01), disease of a higher histologic grade (p = 0.03), lymphovascular invasion (LVI) (p < 0.0001), a greater number of positive ALN (p < 0.0001), extranodal invasion (p < 0.0001), and macroscopic ALN metastases (p < 0.0001). With a median follow-up of 7 years, PMRT and no-PMRT groups were similar in LRR (p = 0.57), RFS (p = 0.70), and OS (p = 0.28). On multivariate analysis of the no-PMRT group, age ≤50 years (p = 0.002) and presence of LVI (p < 0.0001) were associated with LRR. Stratified by age and LVI, patients ≤50 years old and with LVI had the highest 5-year LRR, 10.1 versus 1.1 %, than in patients >50 years old without LVI (p < 0.001).

Conclusions

By using clinicopathologic features, clinicians delivered PMRT to a select group of patients with T1–T2 tumors and 1 to 3 positive ALN, resulting in similarly low rates of 5-year LRR. Among patients not receiving PMRT, age ≤50 years and LVI were associated with increased LRR rates and warrant PMRT consideration.     

Vitamin D Status and Bone Mineral Density Changes During Alendronate Treatment in Postmenopausal Osteoporosis

Vitamin D supplementation is recommended for women with osteoporosis. In the FOCUS-D trial comparing the combination tablet alendronate plus vitamin D₃ 5,600 IU (ALN/D) with standard care (SC) prescribed by patients’ personal physicians, ALN/D was more effective in improving serum 25(OH)D and bone turnover markers by 6 months and increasing spine and hip bone mineral density (BMD) after 1 year than SC. This post hoc analysis examined the relationship between BMD gain and 25(OH)D in women in SC receiving alendronate (SC/ALN, n = 134, 52 % of the SC group) and in the ALN/D group (n = 257). At baseline, participants were of mean age 73 years and 72 % were Caucasian, with a mean 25(OH)D of 14.9 ng/mL. In the SC/ALN group, most received vitamin D, although intake of vitamin D varied extensively (51 % received <400 μg/day). In this group, end-of-study 25(OH)D correlated positively with mean percent increases from baseline in lumbar spine and femoral neck BMD [Pearson correlation coefficients (95 % CI) = 0.23 (0.02–0.41) and 0.24 (0.03–0.41), respectively]. Baseline 25(OH)D correlated with increases in only lumbar spine BMD [Pearson correlation coefficient (95 % CI) = 0.22 (0.01–0.40)]. No correlations between mean BMD change and 25(OH)D were seen with ALN/D. In conclusion, in postmenopausal women with osteoporosis and low 25(OH)D receiving alendronate and a wide range of vitamin D doses, the increase in lumbar spine and femoral neck BMD was positively correlated with serum 25(OH)D achieved by the end of the study and, to some extent, with 25(OH)D concentrations at baseline. The degree of success of alendronate therapy for osteoporosis may depend on the vitamin D status of patients.