The relationship between length of denosumab treatment for postmenopausal osteoporosis and serum TRAcP5b measured six months after the last injection.

To test the hypothesis that during treatment with denosumab osteomorphs and precursors recycle to higher number of osteoclasts with time, we measured TRAcP5b in serum taken 6 months after the last injection in postmenopausal women treated for 1-10 years. Serum TRAcP5b values were not related to time of exposure to denosumab. PURPOSE: In women with postmenopausal osteoporosis the aetiology of the observed inverse relationship between duration of denosumab (Dmab) therapy and bone loss after its discontinuation is currently unknown. In studies in mice inhibition of RANKL is associated with an increase in osteomorphs and osteoclast precursors that recycle into osteoclasts and may accumulate with time. We hypothesized that longer inhibition of RANKL by Dmab will be followed by the synchronous formation of a larger number of osteoclasts after stopping treatment. To test this hypothesis, we measured serum TRAcP5b, a marker of osteoclast numbers, in postmenopausal women treated with Dmab for different periods of time up to 10 years. METHODS: TRAcP5b, C-terminal telopeptide of type 1 collagen (CTX) and procollagen type 1 N-terminal propeptide (P1NP) were measured at 6.0 months ± 15 days after last Dmab injection in 59 women who had received Dmab for 4.0 ± 2.3 years (range 1-10 years). Of these, 38 were treatment naïve (group 1) and 21 had received other treatments prior Dmab (group 2). RESULTS: Duration of Dmab treatment was not related to serum TRAcP5b values or to TRAcP5b/CTX ratio either in the whole cohort or in each of the two groups separately. In contrast, serum TRAcP5b values were significantly correlated with serum CTX values (rs = 0.619; p < 0.001), but not with serum P1NP values or BMD at all skeletal sites. CONCLUSION: Our observations indicate that serum TRAcP5b, measured at 6 months after a Dmab injection, is not a useful early marker for time-dependent increased accumulation of osteoclasts in humans and for identification of patients at risk for a higher rebound increase in bone resorption.

The Five-Year Effect of a Single Zoledronate Infusion on Bone Mineral Density Following Denosumab Discontinuation in Women with Postmenopausal Osteoporosis.

The long-term effects of zoledronate treatment in women with postmenopausal osteoporosis who stop denosumab therapy when they become osteopenic are not known. In a prospective, randomized, controlled clinical trial we previously reported that a single intravenous infusion of zoledronate 5 mg given to such patients 6 months after the last denosumab injection effectively prevents bone loss in the majority of them for up to 3 years. The study was extended for an additional 2 years and included all 19 patients from one Trial Site of the total 27 patients originally randomized in the zoledronate arm. Baseline characteristics of this cohort treated with denosumab for 2.4 ± 0.2 years were not different from those of the whole initial cohort or from the patients who did not participate in this extension. At the end of 5 years 7 patients had become again osteoporotic requiring additional treatment, 9 remained osteopenic while 3 did not complete the study extension. Thus, more than half of the osteoporotic women who became osteopenic with denosumab treatment and stopped it, maintained the BMD gains 5 years after a single zoledronate infusion with no additional treatment. Whether these results are also applicable to patients treated with denosumab for longer periods remains to be established.

Increased Bone Resorption during Lactation in Pycnodysostosis.

Pycnodysostosis, a rare autosomal recessive skeletal dysplasia, is caused by a deficiency of cathepsin K. Patients have impaired bone resorption in the presence of normal or increased numbers of multinucleated, but dysfunctional, osteoclasts. Cathepsin K degrades collagen type I and generates N-telopeptide (NTX) and the C-telopeptide (CTX) that can be quantified. Levels of these telopeptides are increased in lactating women and are associated with increased bone resorption. Nothing is known about the consequences of cathepsin K deficiency in lactating women. Here we present for the first time normalized blood and CTX measurements in a patient with pycnodysostosis, exclusively related to the lactation period. In vitro studies using osteoclasts derived from blood monocytes during lactation and after weaning further show consistent bone resorption before and after lactation. Increased expression of cathepsins L and S in osteoclasts derived from the lactating patient suggests that other proteinases could compensate for the lack of cathepsin K during the lactation period of pycnodysostosis patients.

Influence of subject discontinuation on long-term nonvertebral fracture rate in the denosumab FREEDOM Extension study.

BACKGROUND: Denosumab treatment for up to 8 years in the FREEDOM study and Extension was associated with low fracture incidence. It was not clear whether subjects who discontinued during the study conduct had a higher risk of fracture than those who remained enrolled, thereby underestimating the true fracture risk for the entire trial cohort. Thus, we explored the influence of early withdrawals on nonvertebral fracture incidence during the Extension study. METHODS: To understand the potential effect of depletion of susceptible subjects on fracture incidence, we first evaluated subject characteristics in patients who were enrolled in the Extension vs those who were not. We subsequently employed a Kaplan-Meier multiple imputation (KMMI) approach to consider subjects who discontinued as if they remained enrolled with a 0%, 20%, 50%, and 100% increase in fracture risk compared with participants remaining on study. RESULTS: Extension enrollees were generally similar to nonparticipants in median age (71.9 and 73.1 years, respectively), mean total hip bone mineral density T-score (-1.9 and -2.0, respectively), and probability of fracture risk by Fracture Risk Assessment Tool (FRAX®) at FREEDOM baseline (16.9% and 17.7% for major osteoporotic fracture and 6.7% and 7.4% for hip fracture, respectively). When we assumed a doubled fracture risk (100% increase) after discontinuation in KMMI analyses, nonvertebral fracture rate estimates were only marginally higher than the observed rates for both the crossover group (10.32% vs 9.16%, respectively) and the long-term group (7.63% vs 6.63%, respectively). CONCLUSION: The observation of continued denosumab efficacy over 8 years of treatment was robust and does not seem to be explained by depletion of susceptible subjects. TRIAL REGISTRATION: ClincalTrials.gov registration number NCT00523341 ; registered August 30, 2007.

Sclerostin Inhibition in the Management of Osteoporosis.

The recognition of the importance of the Wnt-signaling pathway in bone metabolism and studies of patients with rare skeletal disorders characterized by high bone mass identified sclerostin as target for the development of new therapeutics for osteoporosis. Findings in animals and humans with sclerostin deficiency as well as results of preclinical and early clinical studies with sclerostin inhibitors demonstrated a new treatment paradigm with a bone building agent for the management of patients with osteoporosis, the antifracture efficacy, and long-term tolerability of which remain to be established in on-going phase III clinical studies. In this article we review the currently available preclinical and clinical evidence supporting the use of sclerostin inhibitors in osteoporosis.

Similarities and Differences in the Management of Patients with Osteoporotic Vertebral Fractures and Those with Rebound-Associated Vertebral Fractures Following Discontinuation of Denosumab.

Rebound-associated vertebral fractures (RVFx) following denosumab discontinuation are typically multiple, are commonly associated with acute sharp pain, increase the risk of imminent fractures, and are pathogenetically different from common osteoporotic vertebral fractures (VFx). A clinically relevant question is whether patients with RVFx should be managed differently from patients with osteoporotic VFx. To address this question, we performed a systematic search of the PubMed database, and we reviewed current evidence on the optimal management of patients with RVFx. For pain relief of patients with RVFx, potent analgesics, often opioids, are essential. Information on the effectiveness of braces in these patients is scarce. Vertebroplasty and kyphoplasty are strongly contraindicated as they confer a substantial risk for new VFx. Exercise may be helpful, but again evidence is lacking. In contrast to patients with osteoporotic VFx, in whom initial treatment with bone-forming agents is recommended, patients with RVFx should initiate treatment with potent antiresorptives. To summarize, patients who have sustained RVFx following denosumab discontinuation are at a very high risk for new fractures, especially VFx. The management of such patients requires a multidisciplinary approach that should not be restricted to pain relief and administration of antiosteoporotic medication, but should also include back protection, early mobilization, and appropriate exercise.

Inhibition of cathepsin K for treatment of osteoporosis.

Cathepsin K is the protease that is primarily responsible for the degradation of bone matrix by osteoclasts. Inhibitors of cathepsin K are in development for treatment of osteoporosis. Currently available antiresorptive drugs interfere with osteoclast function. They inhibit both bone resorption and formation, due to the coupling between these processes. Cathepsin K inhibitors, conversely, target the resorption process itself and may not interfere with osteoclast stimulation of bone formation. In fact, when cathepsin K is absent or inhibited in mice, rabbits, or monkeys, bone formation is maintained or increased. In humans, inhibition of cathepsin K is associated with sustained reductions in bone resorption markers but with smaller and transient reductions in bone formation markers. The usefulness of cathepsin K inhibitors in osteoporosis is now being examined in phase 2 and phase 3 clinical trials of postmenopausal osteoporotic women.

Prevalence of FRAX risk factors and the osteoporosis treatment gap among women ≥ 70 years of age in routine primary care across 8 countries in Europe.

We studied whether elderly women at risk for fractures receive primary care treatment to prevent fracture. We found that across Europe, women at risk are often not identified, and less than half of such women receive appropriate treatment. Finally, women diagnosed with osteoporosis are much more likely to receive treatment. PURPOSE: To examine the relationship between risk factors for fragility fracture (FF) and osteoporosis (OP) treatment gap in elderly women across Europe, and compare the prevalence of risk factors between countries. METHODS: Demographic and clinical information was collected from women ≥ 70 years visiting primary care physicians in Belgium, France, Germany, Ireland, Poland, Slovakia, Switzerland, and the UK. Increased risk of FF was defined by the presence of 1 or more criteria (history of fracture, 10-year fracture probability, or T-score ≤ - 2.5). RESULTS: There were 3798 women in total. Treatment gap (proportion at increased risk of FF not receiving treatment for OP) varied from 53.1 to 90.8% across countries, and the proportion of patients at increased risk of FF varied from 41.2 to 76.1%. Across countries, less than 50% of patients with increased risk of FF had a diagnosis of OP. Previous fracture was the most common risk factor, with similar prevalence across most countries; other risk factors varied widely. The treatment gap was reduced in patients with an OP diagnosis in all countries, but this reduction varied from 36.5 to 79.4%. The countries with the lowest rates of bone densitometry scans (Poland, France, and Germany; 8.3-12.3%) also had the highest treatment gap (82.2 to 90.8%). CONCLUSIONS: This study highlights differences across Europe in clinical risk factors for fracture, rates of densitometry scanning, and the rates of OP diagnosis. More emphasis is needed on risk assessment to improve the identification and treatment of elderly women at risk for fracture.

Targeting sclerostin as potential treatment of osteoporosis.

In recent years, study of rare bone diseases has led to the identification of signalling pathways that regulate bone formation and provided targets for the development of novel therapeutic agents to stimulate bone formation in patients with osteoporosis. Studies of two bone sclerosing dysplasias, sclerosteosis and van Buchem disease led to the identification of sclerostin, a negative regulator of bone formation. Sclerostin binds to LRP5/6 and inhibits Wnt signalling, but its precise molecular mechanism of action is not yet known. Its expression is restricted in the skeleton to osteocytes and is modified by mechanical loading and parathyroid hormone treatment. Sclerostin deficiency reproduces the findings of the human diseases in mice, while sclerostin excess leads to bone loss and reduced bone strength. An antibody to sclerostin increased bone formation dramatically at all bone envelopes in ovariectomised rats and intact monkeys, without affecting bone resorption and improved bone strength. In initial human studies, a single injection of the antibody to postmenopausal women increased serum P1NP and transiently decreased serum CTX. Clinical phase II studies with this antibody are currently underway.

No effect of rosuvastatin in the zoledronate-induced acute-phase response.

The acute-phase response (APR) is frequently observed in patients treated with intravenous (iv) zoledronate (ZOL). We investigated whether a short course of rosuvastatin (ROSU) could attenuate the ZOL--induced APR through blocking the mevalonate pathway at a proximal level. Twenty-eight osteoporotic postmenopausal women with no prior bisphosphonate use (mean age 65.3 ± 1.9 years) were subjected to ZOL iv infusion. Patients were randomly assigned into either a ROSU+ group (n = 12), which received ROSU 10 mg/day starting 5 days before the infusion of ZOL for a total period of 11 days, or a ROSU- group (n = 16), which did not receive ROSU. The visual analog pain scale (VAS) for musculoskeletal symptoms and body temperature was used to define clinically APR. In addition, white blood cell (WBC) count, leukocytic subpopulations, and C-reactive protein (CRP) were obtained before and 48 h following the infusion. Seven (58.3%) patients in the ROSU+ group and 13 (81.3%) in the ROSU- group experienced APR (P = not significant). No difference was found in fever and VAS measurements. CRP and granulocytes increased significantly in both groups; WBC count increased, while lymphocytes and eosinophils decreased significantly only in the ROSU- group. In a post hoc analysis of only patients with an APR, all laboratory parameters exhibited a similar significant change solely within the ROSU- group. In conclusion, our data suggest that a short course of ROS at this dose cannot prevent the ZOL-induced APR among osteoporotic women. Milder changes in acute-phase laboratory parameters in ROSU+ patients suggest that studies with higher doses may be warranted.

Joint Official Positions of the International Society for Clinical Densitometry and International Osteoporosis Foundation on FRAX(®). Executive Summary of the 2010 Position Development Conference on Interpretation and use of FRAX® in clinical practice.

The International Society for Clinical Densitometry (ISCD) and the International Osteoporosis Foundation (IOF) convened the FRAX(®) Position Development Conference (PDC) in Bucharest, Romania, on November 14, 2010, following a two-day joint meeting of the ISCD and IOF on the "Interpretation and Use of FRAX(®) in Clinical Practice." These three days of critical discussion and debate, led by a panel of international experts from the ISCD, IOF and dedicated task forces, have clarified a number of important issues pertaining to the interpretation and implementation of FRAX(®) in clinical practice. The Official Positions resulting from the PDC are intended to enhance the quality and clinical utility of fracture risk assessment worldwide. Since the field of skeletal assessment is still evolving rapidly, some clinically important issues addressed at the PDCs are not associated with robust medical evidence. Accordingly, some Official Positions are based largely on expert opinion. Despite limitations inherent in such a process, the ISCD and IOF believe it is important to provide clinicians and technologists with the best distillation of current knowledge in the discipline of bone densitometry and provide an important focus for the scientific community to consider. This report describes the methodology and results of the ISCD-IOF PDC dedicated to FRAX(®).

The Duration of Denosumab Treatment and the Efficacy of Zoledronate to Preserve Bone Mineral Density After Its Discontinuation.

CONTEXT: Zoledronate is used to prevent bone loss following denosumab discontinuation but its efficacy differs among studies. OBJECTIVE: To test if the duration of denosumab treatment affects the efficacy of subsequent zoledronate infusion. METHODS: This multicenter, prospective cohort study, conducted at 2 Greek and 1 Dutch bone centers, included 47 postmenopausal women (n = 47) who received a single zoledronate infusion 6 months after the last denosumab injection and then were followed for 1 year. Twenty-seven women received ≤ 6 denosumab injections (≤ 6 Group) and 20 received > 6 denosumab injections (> 6 Group). The main outcome measure was changes in lumbar spine (LS) bone mineral density (BMD). RESULTS: At 12 months LS-BMD values were maintained in the ≤ 6 Group (0.98 ±â€…0.10 to 0.99 ±â€…0.9 g/cm2, P = 0.409) but decreased significantly in the > 6 Group (1.0 ±â€…0.11 to 0.93 ±â€…0.12 g/cm2, P < 0.001). The percent change of LS-BMD of the ≤ 6 Group (+1.0%) was significantly different (P < 0.001) from the change of the > 6 Group (-7.0%). In the whole cohort, the duration of denosumab treatment was negatively correlated with the percentage change of LS-BMD (rs = -0.669, P < 0.001) but not with the change of femoral neck (FN)-BMD. Bone turnover markers increased in all patients 6 months following zoledronate administration with no difference between the 2 groups. CONCLUSION: The duration of denosumab treatment significantly affects the efficacy of subsequent zoledronate infusion to maintain BMD gains. Frequent follow-up of patients treated with denosumab longer than 3 years is advisable as additional therapeutic interventions may be needed.

Incidence of Hip and Subtrochanteric/Femoral Shaft Fractures in Postmenopausal Women With Osteoporosis in the Phase 3 Long-Term Odanacatib Fracture Trial.

We prospectively assessed, with predefined criteria, the location and rates of all femur fractures (hip, subtrochanteric/femoral shaft [ST/FS], including atypical [AFF] and distal fractures) in women at increased fracture risk during treatment with the cathepsin K inhibitor, odanacatib (ODN), or placebo over 5 years in the Long-Term ODN Fracture Trial (LOFT and LOFT Extension [NCT00529373, EudraCT 2007-002693-66]). ODN was an investigational antiresorptive agent previously in development as an osteoporosis treatment that, unlike bisphosphonates, reduces bone formation only transiently. Women aged ≥65 years with a bone mineral density (BMD) T-score ≤-2.5 at the total hip (TH) or femoral neck (FN) or with a radiographic vertebral fracture and T-scores ≤-1.5 at the TH or FN were randomized (1:1) to receive ODN 50 mg/week or placebo. All patients received vitamin D3 (5600 IU/week) and calcium (total 1200 mg/d); the analysis included 16,071 women. Rates of all adjudicated low-energy femoral fractures were 0.38 versus 0.58/100 patient-years for ODN and placebo, respectively (hazard ratio [HR] = 0.65; 95% confidence interval [CI] 0.51-0.82; nominal p < .001), and for low-energy hip fractures were 0.29 versus 0.56/100 patient-years, respectively (HR = 0.52; 95% CI 0.40-0.67; p < .001). The cumulative incidence of combined hip and ST/FS or hip fractures alone in the ODN group was consistently lower than in the placebo group (1.93% versus 3.11% for combined fractures and 1.53% versus 3.03% for hip fractures at 5 years, respectively). However, low-energy ST/FS fractures were more frequent in ODN-treated women than in placebo-treated women (24 versus 6, respectively). Among these, 12 fractures were adjudicated as AFF in 10 patients treated with ODN (0.03/100 patient-years) compared with none in the 6 placebo-treated women (estimated difference 0.03; 95% CI 0.02-0.06). These results provide insight into possible pathogeneses of AFF, suggesting that the current criteria for diagnosing these fractures may need to be reconsidered. © 2021 American Society for Bone and Mineral Research (ASBMR)..

First missense mutation in the SOST gene causing sclerosteosis by loss of sclerostin function.

Sclerosteosis is a rare bone dysplasia characterized by greatly increased bone mass, especially of the long bones and the skull. Patients are tall, show facial asymmetry and often have syndactyly. Clinical complications are due to entrapment of cranial nerves. The disease is thought to be due to loss-of-function mutations in the SOST gene. The SOST gene product, sclerostin, is secreted by osteocytes and transported to the bone surface where it inhibits osteoblastic bone formation by antagonizing Wnt signaling. In a small Turkish family with sclerosteosis, we identified a missense mutation (c.499T>C; p.Cys167Arg) in exon 2 of the SOST gene. This type of mutation has not been previously reported and using different functional approaches, we show that it has a devastating effect on the biological function of sclerostin. The affected cysteine is the last cysteine residue of the cystine-knot motif and loss of this residue leads to retention of the mutant protein in the ER, possibly as a consequence of impaired folding. Together with a significant reduced ability to bind to LRP5 and inhibit Wnt signaling, the p.Cys167Arg mutation leads to a complete loss of function of sclerostin and thus to the characteristic sclerosteosis phenotype.

Sclerostin is an osteocyte-expressed negative regulator of bone formation, but not a classical BMP antagonist.

Sclerosteosis, a skeletal disorder characterized by high bone mass due to increased osteoblast activity, is caused by loss of the SOST gene product, sclerostin. The localization in bone and the mechanism of action of sclerostin are not yet known, but it has been hypothesized that it may act as a bone morphogenetic protein (BMP) antagonist. We show here that SOST/sclerostin is expressed exclusively by osteocytes in mouse and human bone and inhibits the differentiation and mineralization of murine preosteoblastic cells (KS483). Although sclerostin shares some of the actions of the BMP antagonist noggin, we show here that it also has actions distinctly different from it. In contrast to noggin, sclerostin did not inhibit basal alkaline phosphatase (ALP) activity in KS483 cells, nor did it antagonize BMP-stimulated ALP activity in mouse C2C12 cells. In addition, sclerostin had no effect on BMP-stimulated Smad phosphorylation and direct transcriptional activation of MSX-2 and BMP response element reporter constructs in KS483 cells. Its unique localization and action on osteoblasts suggest that sclerostin may be the previously proposed osteocyte-derived factor that is transported to osteoblasts at the bone surface and inhibits bone formation.

The majority of the genetic risk for Paget's disease of bone is explained by genetic variants close to the CSF1, OPTN, TM7SF4, and TNFRSF11A genes.

Paget's disease of bone (PDB) is one of the most frequent metabolic bone disorders (1-5%), next to osteoporosis, affecting individuals above age 55. Sequestosome1 mutations explain a part of the PDB patients, but still the disease pathogenesis in the remaining PDB patients is largely unknown. Therefore, association studies investigating the relationship between genetic polymorphisms and sporadic PDB have been performed to find the genetic risk variants. Previously such studies indicated a role of the OPG and RANK gene. The latter was recently confirmed in a genome-wide association study (GWAS) which also indicated the involvement of chromosomal regions harbouring the CSF1 and OPTN gene. In this study, we sought to replicate these findings in a Belgian and a Dutch population. Similar significant results were obtained for the single nucleotide polymorphisms and the haplotypes. The most significant results are found in the CSF1 gene region, followed by the OPTN and TNFRSF11A gene region (p values ranging from 1.3 × 10(-4) to 3.8 × 10(-8), OR = 1.523-1.858). We next obtained significant association with a polymorphism from the chromosomal region around the TM7SF4 gene (p = 2.7 × 10(-3), OR = 1.427), encoding DC-STAMP which did not reach genome-wide significance in the GWAS, but based on its function in osteoclasts it can be considered a strong candidate gene. After meta-analysis with the GWAS data, p values ranged between 2.6 × 10(-4) and 8.8 × 10(-32). The calculated cumulative population attributable risk of these four loci turned out to be about 67% in our two populations, indicating that most of the genetic risk for PDB is coming from genetic variants close to these four genes.

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

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

Zoledronate decreases CTLA-4 in vivo and in vitro independently of its action on bone resorption.

Acute phase response (APR) following intravenous zoledronate (ZOL) administration is related to activation and increased proliferation of γδ T cells, attributed to the molecular mechanism of action of nitrogen-containing bisphosphonates (N-BPs). ZOL, however, has also been reported to inhibit the proliferation of regulatory T cells in vitro and to reduce the expression of Cytotoxic T-Lymphocyte Antigen-4 (CTLA-4), a negative regulator of T cell activation that is increased in patients with autoimmune diseases. There are, however, no data on the relationship between ZOL treatment and soluble(s)CTLA-4 either in vivo in relevant patient populations or in vitro with the use of assays relevant to the mechanism of action of N-BPs. The objectives of the present study were firstly, to characterize the ZOL-induced APR in patients with inflammatory rheumatic diseases (IRDs) and its relationship with changes in circulating sCTLA-4 and secondly, to investigate the effects of ZOL on CTLA-4 production and expression by peripheral blood mononuclear cells (PBMCs). We studied 10 postmenopausal women with IRDs treated with intravenous ZOL 5 mg. Five women experienced APR (APR+) associated with significant decreases in blood lymphocytes and increases in granulocytes and serum CRP. Serum sCTLA-4 values were increased in all patients before ZOL administration and decreased significantly 72 h after the ZOL infusion (from 30.0 ± 2.9 to 6.3 ± 1.8 ng/ml; p < 0.001) with no differences between APR+ and APR- patients. Consistent with the results of the in vivo study, ZOL (1 µM) decreased the production of sCTLA-4 by 87% and 57% after 3 and 5 days in cultures of peripheral blood mononuclear cells (PBMCs) in vitro, respectively, and inhibited the expression of both cytoplasmic and membrane-bound CTLA-4. Our results reveal a novel immunoregulatory action of ZOL that is not related to its action on bone resorption but might be associated with reported clinically significant extraskeletal outcomes of ZOL treatment.

The three-year effect of a single zoledronate infusion on bone mineral density and bone turnover markers following denosumab discontinuation in women with postmenopausal osteoporosis.

INTRODUCTION: In women with postmenopausal osteoporosis denosumab discontinuation is associated with rapid bone loss that could be potentially prevented by a single zoledronate infusion for two years. The longer-term effects, however, of zoledronate treatment are unknown. We aimed to study the effect of a single zoledronate infusion during the third year following denosumab discontinuation, in initially treatment-naive postmenopausal women who became osteopenic after 2.4 ± 0.2 years of denosumab therapy. METHODS: We report the 1-year follow-up results of a single arm observational extension of a previously reported 2-year multicenter prospective randomized clinical trial. The primary endpoint of this extension was the change in lumbar spine bone mineral density (LS-BMD); secondary endpoints were changes in femoral neck (FN)-BMD and markers of bone turnover (BTM) during the 3rd year from the zoledronate infusion. Changes are presented as mean and SEM. RESULTS: LS-BMD did not change significantly at year 3 compared to year 2 (-1.35 ± 1.1%, p = 1.00) and compared to baseline (-1.96 ± 1.44%, p = 1.00). FN-BMD values did not change while serum P1NP values decreased and CTX values remained unchanged during the third-year of the follow-up. In 4 of the 23 studied women BMD values returned to the osteoporotic range at 3 years. CONCLUSIONS: A single i.v. infusion of zoledronate 5 mg, given 6 months after the last injection of denosumab therapy maintains for three years BMD gains in the majority of patients previously treated with denosumab for an approximate period of 2.5 years. Follow-up of patients is, however, recommended because about one-fifth of treated women will require additional antiosteoporotic treatment.