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Keywords:

  • denosumab;
  • osteoporosis;
  • BMD;
  • bone turnover markers;
  • RANKL

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES

Denosumab is a monoclonal antibody to RANKL. In this randomized, placebo-controlled study of 412 postmenopausal women with low BMD, subcutaneous denosumab given every 3 or 6 mo was well tolerated, increased BMD, and decreased bone resorption markers for up to 24 mo. Continued study of denosumab is warranted in the treatment of low BMD in postmenopausal women.

Introduction: Denosumab is a fully human monoclonal antibody that inhibits RANKL, a key mediator of osteoclastogenesis and bone remodeling. This prespecified exploratory analysis evaluated the efficacy and safety of denosumab through 24 mo in the treatment of postmenopausal women with low BMD.

Materials and Methods: Four hundred twelve postmenopausal women with lumbar spine BMD T-scores of −1.8 to −4.0 or femoral neck/total hip T-scores of −1.8 to −3.5 were randomly assigned to receive double-blind, subcutaneous injections of placebo; denosumab 6, 14, or 30 mg every 3 mo; denosumab 14, 60, 100, or 210 mg every 6 mo; or open-label oral alendronate 70 mg once weekly. Outcome measures included BMD at the lumbar spine, total hip, distal one-third radius, and total body; bone turnover markers; and safety.

Results: Denosumab increased BMD at all measured skeletal sites and decreased concentrations of bone turnover markers compared with placebo at 24 mo. At the lumbar spine, BMD increases with denosumab ranged from 4.13% to 8.89%. BMD changes with denosumab 30 mg every 3 mo and ≥60 mg every 6 mo were similar to, or in some cases greater than, with alendronate. The incidence of adverse events was similar in the placebo, denosumab, and alendronate treatment groups. Exposure-adjusted adverse events over 2 yr of treatment were similar to those reported during the first year of treatment.

Conclusions: In these postmenopausal women with low BMD, treatment with denosumab for 2 yr was associated with sustained increases in BMD and reductions in bone resorption markers compared with placebo.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES

Osteoporosis or low bone mass (osteopenia) is a major worldwide public health concern that results in increased risk of fractures.(1) The lifetime risk of any osteoporotic fracture has been estimated to be 40–50% in women and 13–22% in men.(1) The consequences of hip and spine fractures include increased morbidity and mortality.(1–4)

Recent advances in the field of bone physiology have identified RANKL as a critical mediator of bone remodeling. RANKL is a member of the TNF family that has been implicated in the pathogenesis of many bone diseases.(5–7) RANK, the receptor for RANKL, has been identified on the surface of osteoclasts at several stages of differentiation, including prefusion osteoclasts and mature osteoclasts.(5,7) A key regulator of the RANKL–RANK interaction is the soluble cytokine receptor, osteoprotegerin (OPG),(8) a naturally occurring member of the TNF receptor family that competes with RANK to bind RANKL, thus sequestering RANKL and neutralizing its effects.(5–10) Clinical and preclinical evidence suggest that, in many disease states, RANKL is implicated in the bone loss that leads to skeletal fragility and fracture.(6,11–13) Moreover, preclinical studies have shown that RANKL inhibition leads to skeletal benefits that include increases in bone density, volume, and strength.(8,14–18)

Denosumab (AMG 162; Amgen) is a fully human monoclonal antibody (IgG2) that inhibits RANKL with high specificity, mimicking the effects of OPG on RANKL. In a phase 1 clinical trial, a single subcutaneous injection of denosumab resulted in a rapid, dose-dependent, and reversible decrease in the bone resorption marker N-telopeptide measured in the serum and urine.(19) Here we present data from a phase 2, randomized, dose-ranging, placebo- and active-controlled study that was performed to assess the efficacy and safety of denosumab in postmenopausal women with low BMD. The primary analysis of data at 12 mo showed that denosumab increased BMD and decreased markers of bone turnover significantly compared with placebo.(20) The objective of this analysis was to evaluate the efficacy and safety of denosumab after extended exposure for 24 mo.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES

The methods used in this clinical trial for the first 12 mo of treatment were published previously.(20) Those methods are summarized below.

Eligibility criteria

Postmenopausal women up to 80 yr of age were eligible if they had a BMD T-score of −1.8 to −4.0 at the lumbar spine or −1.8 to −3.5 at the femoral neck or total hip. An upper limit of −1.8 was selected to include both osteopenic and osteoporotic populations. Exclusion criteria included the use of bisphosphonates within 12 mo or fluoride within 24 mo; tibolone, PTH or any derivative, systemic glucocorticoids (>5 mg prednisone-equivalent daily for >10 days), inhaled glucocorticoids (>2000 μg daily for >10 days), anabolic steroids, or testosterone within 6 mo; and estrogens, selective estrogen receptor modulators, calcitonin, or calcitriol within 3 mo of enrollment. Women with hyper- or hypoparathyroidism, hyper- or hypothyroidism, hypocalcemia, rheumatoid arthritis, Paget's disease of bone, osteomalacia, creatinine clearance ≤ 35 ml/min as determined using the Cockcroft-Gault equation,(21) malabsorption syndrome, recent long-bone fracture (within 6 mo), more than one grade 1 vertebral fracture, or an osteoporosis-related fracture within the last 2 yr were excluded. Potential subjects were also excluded if BMD could not be measured accurately by DXA.

Institutional review boards approved the study protocol for each participating center, and all subjects provided written informed consent.

Interventions

This randomized, placebo-controlled, dose-ranging study of 412 postmenopausal women with low BMD included eight double-blind treatment groups and one open-label treatment group. Women from 29 study centers in the United States were randomly allocated to receive double-blind placebo or denosumab or to receive open-label alendronate. Subjects received one of the following: placebo subcutaneously every 3 mo; denosumab 6, 14, or 30 mg subcutaneously every 3 mo; denosumab 14, 60, 100, or 210 mg subcutaneously every 6 mo, alternating with placebo to maintain the blinding; or open-label alendronate 70 mg orally once weekly. Randomization was stratified by center, using a randomization schedule prepared by Amgen before the start of the study. The denosumab solution contained denosumab (30 or 70 mg/ml) in 5% sorbitol and 10 mM sodium acetate in water for injection (USP), pH 5.2. Subjects were instructed to take oral supplements containing elemental calcium (1 g) and vitamin D (400 IU) daily.

Outcomes measured

Study visits were scheduled for baseline, 3 days after the first dose, monthly during the first year (as well as 3 days after the 6-mo dose), and every 3 mo during the second year. BMD was measured by DXA (GE Healthcare or Hologic). Lumbar spine (L1–L4) and total hip BMD were measured at baseline and at 1, 3, 6, 12, 18, and 24 mo; distal one-third radius and total body BMD were measured at baseline and at 6, 12, 18, and 24 mo. Quality control and analysis of scans were done at Bio-Imaging Technologies. Serum C-telopeptide (Crosslaps; Nordic Biosciences), urine N-telopeptide (Osteomark), and bone-specific alkaline phosphatase (Tandem-R Ostase, Hybritech or Access Ostase assay; Beckman Coulter) were measured from fasting samples at every visit. Intact PTH (iPTH) levels were assessed (Nichols) at baseline and at 1, 3, 6, 12, 18, and 24 mo. Hematology assessments were made at screening, baseline, and at 1, 2, 3, 6, 12, 18, and 24 mo. Serum chemistries were recorded at screening, baseline, 3 days after the first dose, and at 1, 2, 3, 6, 7, 9, 12, 15, 18, 21, and 24 mo, as well as 3 days after the 6-mo dose. Serum denosumab levels were determined at all study visits except screening. A validated electrochemiluminescent immunoassay was used to detect anti-denosumab binding antibodies at screening, baseline, and at 1, 2, 3, 6, 9, 12, 15, 18, 21, and 24 mo; samples with binding antibodies were later screened for denosumab-neutralizing antibodies by a cell-based assay.(22)

Adverse events included any new or undesirable medical occurrence or worsening of an existing condition that occurred after the start of study treatment. Reports of adverse events were collected spontaneously and in response to nondirected questioning at each study visit.

Statistical analysis

Summary statistics of demographic and baseline characteristics were calculated for all randomized subjects. The primary outcome was percent change from baseline in lumbar spine BMD at month 12, as has been previously reported.(20) Key outcomes for this analysis included percentage change from baseline in BMD at the lumbar spine, total hip, distal one-third radius, and total body (minus head) at 24 mo; percentage change from baseline in bone turnover markers at 24 mo; and safety. Percentage changes from baseline for BMD and bone turnover markers were calculated for all subjects with nonmissing data at baseline and the time-point of interest and were compared across dose groups. The mean percentage changes from baseline in BMD were analyzed using analysis of covariance (ANCOVA) models, with treatment group as the main effect and geographical center location and baseline BMD value as covariates. A repeated-measures model was also used as a sensitivity analysis. The mean percentage changes in BMD from month 12 to month 24 were analyzed in a similar manner. Percentage changes in bone turnover markers were skewed and thus are summarized using medians. The p values for the pairwise comparisons between the denosumab groups and placebo within an endpoint were adjusted for multiple comparisons using Hochberg's procedure.(23) Unadjusted p values were reported for comparisons relative to alendronate. Comparisons at 24 mo with respect to efficacy analyses were exploratory, using a critical p value of 0.001 for statistical significance, because the type 1 error allocation was planned and applied at the 12-mo analysis. Safety analyses included all subjects who received at least one dose of study drug. Comparisons among the denosumab, placebo, and alendronate groups with respect to safety analyses were based on Fisher's exact test; p values are nominal. Sample size calculation was determined as previously described.(20)

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES

Study participants

Data were collected from May 2002 to April 2005. Disposition of study subjects is summarized in Fig. 1. Of the 412 women randomly assigned to treatment groups (46 placebo subjects, 319 denosumab subjects, and 47 alendronate subjects), 406 (98.5%) subjects received at least one dose of study drug, and 337 (81.8%) subjects completed 24 mo of study. The most common reasons for early discontinuation were consent withdrawal (11.2%) and adverse events (3.2%).

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Figure FIG. 1.. Disposition of study subjects. CW, consent withdrawn; AE, adverse event; BMD, did not meet BMD criteria.

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Baseline demographics and clinical characteristics of randomized subjects were similar among treatment groups (Table 1). Distribution of BMD and bone turnover markers was also similar among the groups. The mean (SD) age of subjects was 62.5 (8.1) yr. The mean BMD T-score of the lumbar spine at baseline was −2.2 in the placebo group and −2.0 in the alendronate group, with a range from −2.0 to −2.3 in the denosumab dose cohorts. Prior use of osteoporosis therapy was balanced among groups.

Table Table 1.. Baseline Demographics and Characteristics
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Efficacy

BMD:

Denosumab treatment for 24 mo was associated with significant increases from baseline in BMD compared with placebo. At the lumbar spine, BMD increases ranged from 4.13% to 8.89% compared with a −1.18% change from baseline in the placebo group (p < 0.001 for all doses of denosumab versus placebo at 24 mo). The percentage changes from baseline in lumbar spine BMD for all denosumab dose cohorts were significantly greater than those for placebo (p < 0.001) from month 3 to month 24 (Figs. 2A and 3A). At 24 mo, all doses of denosumab were associated with significant increases from baseline compared with placebo (p < 0.001) for BMD of the total hip (Figs. 2B and 3B), distal one-third radius (Figs. 2C and 3C), and total body (Figs. 2D and 3D).

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Figure FIG. 2.. Comparison of percentage change in BMD and laboratory parameters with denosumab 3-mo regimens, alendronate, and placebo (□, placebo; •, denosumab 6 mg; ▴, denosumab 14 mg; ♦, denosumab 30 mg; ○, alendronate 70 mg weekly). Between-group differences at p < 0.05 were observed based on ANCOVA model adjusting for treatment group, geographical location, and baseline value as follows: adenosumab 6 mg vs. placebo; bdenosumab 14 mg vs. placebo; cdenosumab 30 mg vs. placebo; dalendronate vs. placebo. Error bars denote SE.

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Figure FIG. 3.. Comparison of percentage change in BMD and laboratory parameters with denosumab 6-mo regimens, alendronate, and placebo (□, placebo; •, denosumab 14 mg; ▴, denosumab 60 mg; ♦, denosumab 100 mg; ▪, denosumab 210 mg; ○, alendronate 70 mg weekly). Between-group differences at p < 0.05 were observed based on ANCOVA model adjusting for treatment group, geographical location, and baseline value as follows: adenosumab 14 mg vs. placebo; bdenosumab 60 mg vs. placebo; cdenosumab 100 mg vs. placebo; ddenosumab 210 mg vs. placebo; ealendronate vs. placebo. Error bars denote SE.

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At 24 mo, alendronate treatment also increased BMD significantly compared with placebo at the lumbar spine (p < 0.001; Figs. 2A and 3A), total hip (p < 0.001 Figs. 2B and 3B), distal one-third radius (p = 0.009; Figs. 2C and 3C), and total body (p < 0.001; Figs. 2D and 3D). When the active treatment groups were compared at 24 mo, denosumab treatment was associated with similar or greater increases in BMD than alendronate at all four skeletal sites, with the exception of the 14-mg 6-mo dose, in which the change in lumbar spine BMD was less than with alendronate treatment (p = 0.02). Neither baseline BMD nor baseline serum C-telopeptide had an impact on the BMD response to denosumab or alendronate.

The overall conclusions from the repeated-measures model were consistent with the results from the ANCOVA model as described above.

BMD change between 12 and 24 mo with denosumab treatment was assessed. Because the 60-mg 6-mo dose is being further studied in a phase 3 fracture prevention trial, changes in BMD from 12 to 24 mo were examined for this dose group. BMD increased from 12 to 24 mo by [LS mean (SE)] 2.75% (0.66%) at the lumbar spine (p < 0.001), 1.50% (0.47%) at the total hip (p = 0.001), and 2.23% (0.69%) at the femoral neck (p = 0.001), with changes of 0.52% (0.67%) (p = 0.440) at the distal one-third radius and 0.20% (0.60%) (p = 0.737) at the total body.

Bone turnover markers:

During the second year of treatment, denosumab maintained reductions in serum C-telopeptide and urine N-telopeptide/creatinine compared with placebo, consistent with the reductions seen during the first year of treatment. Statistically significant (p < 0.001) median percent reductions from baseline in serum C-telopeptide and urine N-telopeptide/creatinine relative to placebo were observed for all doses and time-points except the 14-mg 6-mo dose group, for which values approached baseline levels at the time-points just before the next denosumab dose (Figs. 2E, 2F, 3E, and 3F).

Reductions in bone-specific alkaline phosphatase levels during the second year of denosumab treatment remained consistent compared with the first year of treatment and statistically greater compared with the placebo group (p ≤ 0.002; Figs. 2G and 3G).

Alendronate treatment also maintained sustained reductions in levels of bone turnover markers during the second year (Figs. 2E–2G and 3E–3G). Reductions in serum C-telopeptide by alendronate were less than those observed with the higher doses of denosumab, whereas reductions in bone-specific alkaline phosphatase were similar with alendronate and denosumab treatment.

Calcium and PTH levels:

Mean albumin-adjusted serum calcium levels showed early, small decreases from baseline, as previously reported.(20) In the second year of treatment, no denosumab-treated subjects had albumin-adjusted serum calcium levels <8.6 mg/dl, and no subjects manifested symptomatic hypocalcemia. The mean plasma concentration of iPTH increased substantially 1 mo after the first dose of denosumab.(20) After the first 6 mo, plasma iPTH levels were measured every 6 mo (i.e., they were not measured at 1 mo after dosing); thus, it is not known whether the transient increase in iPTH levels occurred with subsequent doses of denosumab. Mean values for iPTH remained within the normal range at each assessment during the second year of treatment and similar to the month 12 levels.(20)

Safety

Adverse events:

The percentage of subjects who experienced adverse events over 2 yr was generally similar among the placebo, denosumab, and alendronate groups (Table 2). Upper respiratory tract infection was the most common adverse event in the denosumab group (17.4% placebo, 24.2% denosumab, 23.9% alendronate). Other adverse events that occurred with >20% frequency in any treatment group were arthralgia (28.3% placebo, 19.1% denosumab, 10.9% alendronate), dyspepsia (6.5% placebo, 10.5% denosumab, 26.1% alendronate), and nausea (4.3% placebo, 11.1% denosumab, 21.7% alendronate). The incidences of hypertension and urinary tract infection were greater in the denosumab group than the placebo group, and the incidences of dyspepsia and osteoarthritis were greater in the open-label alendronate group. Serious adverse events were recorded for 4 (8.7%), 42 (13.4%), and 6 (13.0%) subjects in the placebo, denosumab, and alendronate groups, respectively (Table 3). Six cases of serious adverse events of infections associated with hospitalization were observed in the denosumab group (two cases each of diverticulitis and pneumonia and one case each of atypical pneumonia and labyrinthitis). One death, caused by gastric cancer, occurred during the study in the denosumab 100-mg 6-mo dose cohort. Clinical fractures occurred in 1/46 (2.2%), 21/314 (6.7%), and 2/46 (4.3%) subjects receiving placebo, denosumab, and alendronate, respectively, whereas osteoporotic fractures occurred in 0/46 (0%), 12/314 (3.8%), and 2/46 (4.3%) subjects, respectively.

Table Table 2.. Adverse Events Occurring at a Rate of ≥10% in Any Treatment Group Over 24 Mo*
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Table Table 3.. Serious Adverse Events Through 24 Mo by Treatment Group*
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Analysis of adverse events by exposure-adjusted rates revealed that, among all treatment groups, rates of occurrence of adverse events did not increase with extended time of exposure to study drug. Discontinuation rates because of adverse events during the first and second years were 2.2% and 0% in the placebo group, 1.6% and 1.3% in the denosumab group, and 0% and 6.4% in the alendronate group, respectively.

Other safety outcomes:

Safety analyses identified no clinically relevant changes in either serum chemistry or hematology values. No notable differences among treatment groups in mean values, changes in toxicity grades, or individual patient trends over time were observed. As previously reported, two subjects had transient, non-neutralizing, anti-denosumab-binding antibodies in the first 12 mo.(20) No neutralizing antibodies to denosumab were observed during the first or second year of treatment.

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES

This planned 2-yr analysis of an ongoing clinical trial evaluated the efficacy and safety of denosumab, a fully human monoclonal antibody (IgG2) to RANKL, for the management of postmenopausal women with low BMD. Denosumab treatment increased BMD over a period of 24 mo, and all doses of denosumab were significantly more effective than placebo, which was associated with a decrease in BMD during 24 mo of study. Increases in BMD with the higher doses of denosumab administered every 3 mo or 6 mo were at least comparable to those with open-label oral alendronate taken once daily. Denosumab treatment also produced significant decreases in serum C-telopeptide and urine N-telopeptide/creatinine compared with placebo that were seen as early as 72 h and maintained over 24 mo. Although N-telopeptide values appeared to increase over time during the second year, these changes were within the CV for the assay.

The observed changes in BMD and bone resorption markers with denosumab use over 2 yr are consistent with a reduction in osteoclast-mediated bone resorption through inhibition of RANKL. The release in the suppression of bone turnover markers that occurred at the end of each dosing interval with lower doses of denosumab suggests reversibility in the effect of denosumab on osteoclasts and their precursors.

Although a number of therapies for postmenopausal osteoporosis are available, none specifically target RANKL. Several advantages of denosumab—including an infrequent dosing schedule and an increase in BMD at highly cortical sites—suggest it may have potential advantages over current therapies. Pharmacokinetic studies have shown that concentrations of denosumab persist for several months after injection in postmenopausal women,(19) and 6-mo dosing of denosumab in this study provided durable effects on BMD and bone turnover markers. In addition to increasing BMD at the lumbar spine, denosumab increased BMD at the total hip and distal one-third radius, which are highly cortical sites. Preclinical models of RANKL inhibition have shown significant increases in cortical and trabecular BMD, as well as increases in bone volume and strength.(14–18,24) This clinical trial showed increased BMD and reduced bone turnover with denosumab inhibition of RANKL. Further clinical studies are underway to evaluate bone strength and fracture risk with denosumab treatment in humans.

This study also confirmed the tolerability and safety profile of denosumab from previous reports.(19,20,25) Although only 314 subjects were exposed to denosumab in this study, the injections appeared to be well tolerated, and no safety concerns were evident. The relatively small size of the study and the disproportionately greater number of subjects assigned to denosumab treatment than to placebo or alendronate make it difficult to determine the clinical relevance of the nominal differences observed among treatment groups for some adverse events. The six serious adverse events of infections associated with hospitalization in the denosumab group were common community-acquired infections that were successfully treated with standard antibiotics during uncomplicated hospital courses. The rate of infections remained unchanged from year 1 to year 2 in the denosumab group. No neutralizing antibodies to denosumab were observed over the 2-yr treatment period.

A strength of this study was the use of an active comparator group in addition to a placebo control group, which is unusual for a phase 2 trial. All 3-mo doses of denosumab and all 6-mo doses of 60 mg or more were associated with similar or greater increases in BMD compared with once-weekly alendronate. This study was not powered to compare fracture risk between treatment groups, nor could it determine what levels of bone suppression and BMD increases are optimal for the prevention of fractures. Additional study of these outcomes is warranted. Because of the open-label nature of the alendronate treatment group, definitive conclusions about the relative efficacy and tolerability of denosumab and alendronate cannot be made. Seven subjects (15%) discontinued open-label alendronate treatment in this study. In comparison, double-blind injections of placebo or denosumab were associated with approximately one half as many early discontinuations because of adverse events, but two to three times as many early discontinuations because of consent withdrawal.

Because the rates of discontinuation were comparable for denosumab and placebo, withdrawal of consent to receive denosumab because of an unclassified adverse event seems unlikely. Withdrawal of consent may instead have been driven by the requirement for multiple subcutaneous injections at each study visit and the possibility of being in the placebo arm, an outcome that is not unusual in a long-term placebo-controlled study. In clinical practice, subjects may be more likely to continue treatment with a single subcutaneous injection every 6 mo that has been shown to increase BMD.

Through its unique mechanism of action, denosumab targets the physiological pathway that regulates osteoclastic bone resorption. In this phase 2 study, RANKL inhibition with denosumab reduced bone turnover and increased BMD relative to placebo. Increases in BMD were observed during 2 yr of treatment with denosumab. Subcutaneous administration of denosumab every 3 or 6 mo was well tolerated during this study, enabling most subjects to continue therapy through 2 yr. These findings support the continued study of denosumab for the prevention and treatment of bone loss and fracture risk reduction in postmenopausal women.

In summary, in these postmenopausal women with low BMD, treatment with denosumab for 2 yr was associated with a sustained increase in BMD and a reduction in bone resorption markers compared with placebo. Adverse events and serious adverse events were similar in character and percentage with denosumab compared with placebo. Further study to evaluate long-term safety and efficacy is warranted.

Acknowledgements

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES

This study was supported by a grant from Amgen, which supervised the design and conduct of the study; the collection, management, analysis, and interpretation of the data; and the preparation, review, and approval of the manuscript. Holly Brenza Zoog and Jonathan N Latham provided medical writing assistance on behalf of Amgen. We thank the additional members of the AMG 162 Bone Loss Study Group.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
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