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Keywords:

  • ANABOLICS;
  • OSTEOPOROSIS;
  • BIOCHEMICAL MARKERS OF BONE TURNOVER;
  • DXA;
  • CLINICAL TRIALS

ABSTRACT

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

Two clinical studies were conducted to assess the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple doses (intravenous [iv] and subcutaneous [sc]) of blosozumab in postmenopausal women, including prior/current bisphosphonate (BP) users. In these phase 1, randomized, subject- and investigator-blind, placebo-controlled studies, subjects received escalating doses of blosozumab: single iv doses up to 750 mg, single sc doses of 150 mg, multiple iv doses up to 750 mg every 2 weeks (Q2W) for 8 weeks, multiple sc doses up to 270 mg Q2W for 8 weeks, or placebo. Six subjects were randomized to each dose in the single-dose study (12 to placebo) and up to 12 subjects to each arm in the multiple-dose study. Blosozumab was well tolerated with no safety concerns identified after single or multiple administrations up to 750 mg. Dose-dependent responses were observed in sclerostin, N-terminal propeptide of procollagen type 1, bone-specific alkaline phosphatase, osteocalcin, C-terminal fragment of type 1 collagen, and bone mineral density (BMD) after single and multiple (up to 5) administrations of blosozumab. There was up to a 3.41% (p = 0.002) and up to a 7.71% (p < 0.001) change from baseline in lumbar spine BMD at day 85 after single or multiple administrations of blosozumab, respectively. Prior BP use did not appear to have a clear impact on the effects of single doses of blosozumab when considering bone biomarker and BMD responses. Antibodies to blosozumab were detected by a screening assay, but no patterns with regard to dose or route of administration and no clear impact on blosozumab exposure or PD responses were identified. In summary, blosozumab was well tolerated and exhibited anabolic effects on bone. These findings support further investigation of blosozumab as a potential anabolic therapy for osteoporosis. © 2014 American Society for Bone and Mineral Research.


Introduction

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

Sclerostin, a protein encoded by the SOST gene and produced by osteocytes, negatively regulates osteoblastic bone formation.[1, 2] Loss-of-function mutations in SOST are associated with an autosomal-recessive disorder, sclerosteosis, which is characterized by progressive bone thickening.[3, 4] Individuals with Van Buchem disease, a recessively inherited high bone mass disorder, have a deletion downstream of the SOST gene resulting in reduced expression of sclerostin, which leads to increased bone formation and stronger bones.[3, 5] Targeted deletion of the sclerostin gene in mice results in increased bone formation and bone strength.[6]

In animal studies, treatment with an antisclerostin antibody resulted in increased bone formation, bone mineral density (BMD), and bone strength.[7, 8] In a published clinical study of healthy men and postmenopausal women, Padhi and colleagues disclosed that administration of AMG 785, an antisclerostin monoclonal antibody, resulted in dose-related increases in bone-formation markers and statistically significant increases in BMD.[9]

Blosozumab is a humanized immunoglobulin G4 (IgG4) anti-sclerostin monoclonal antibody, and is being developed as a bone anabolic agent for the treatment of osteoporosis in men and postmenopausal women. Preclinical studies demonstrated that the administration of blosozumab or a mouse/rat chimeric monoclonal antisclerostin antibody promotes bone formation and results in robust improvements in bone microstructure and strength.[10]

The objectives of the described studies were to assess the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple administrations of intravenous (iv) or subcutaneous (sc) blosozumab in healthy postmenopausal women.

Materials and Methods

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

The single-dose study (first 5 cohorts) was a phase 1, randomized, subject- and investigator-blind, placebo-controlled, single-dose, dose-escalation study in postmenopausal women, exploring a dose range of 7.5 to 750 mg as a slow iv infusion (7.5, 25, 75, 225, and 750 mg). Fig. 1A illustrates the overall study design. At each dose level during the dose-escalation phase, subjects received blosozumab or placebo, according to the randomization schedule. In addition, a single cohort of subjects received blosozumab 150 mg or placebo administered by sc injection (cohort 6). Two additional cohorts (cohorts 7 and 8) of postmenopausal women with prior exposure to bisphosphonate (BP) were assigned to 225 mg or 750 mg blosozumab iv, respectively, in an unblinded manner. After study drug administration, all subjects were followed for 12 weeks for safety, PK, and PD assessments.

image

Figure 1. Study designs for the single-dose (A) and 8-week multiple-dose (B) studies. BP = prior bisphosphonate exposure; iv = intravenous; PK = pharmacokinetic; Q2W = once every 2 weeks; Q4W = once every 4 weeks; sc = subcutaneous.

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The multiple-dose study was a phase 1, multicenter, randomized, subject- and investigator-blinded, placebo-controlled, parallel-design study evaluating the safety and tolerability of multiple administrations of blosozumab in postmenopausal women. Based on a review of the single-dose data, a once every 2 weeks (Q2W) and a once every 4 weeks (Q4W) dose regimen were included in the multiple-dose study. Fig. 1B illustrates the overall study design. There were 6 treatment arms, consisting of 3 sc dosing arms (180 mg Q4W, 270 mg Q4W, and 270 mg Q2W), and 2 iv dosing arms (540 mg Q4W and 750 mg Q2W) of blosozumab and a placebo arm (iv and sc study drug [blosozumab or placebo]) was dosed Q2W for all dosing arms (placebo alternating with blosozumab for the Q4W regimens) to maintain the blinding, with the final dose administered at week 8. Subjects were followed for an additional 12 weeks after the final dose of study drug.

The total study duration for each subject was approximately 16 weeks (4-week entry period; single study day; 12-week follow-up) for the single-dose study and 24 weeks (4-week entry period; 8-week treatment period; 12-week follow-up) for the multiple-dose study.

Both studies were conducted in the United States at commercial phase 1 units. They were approved by local ethical review boards, and were conducted in accordance with all applicable regulatory and Good Clinical Practice guidelines and the Declaration of Helsinki. All subjects provided written informed consent before study initiation.

Study subjects

Eligible subjects were overtly healthy postmenopausal females, between the ages of 45 and 70 years (single-dose study), or between 45 and 80 years (multiple-dose study), with a body mass index between 19.0 and 32.0 kg/m2. The recruitment of subjects was based on medical history, screening evaluations (including electrocardiogram, clinical laboratory blood tests, and blood pressure assessment), and physical examination. The baseline BMD evaluation was conducted after all screening requirements had been met; there were no specific BMD entry criteria for any groups in either of the studies. Postmenopausal was defined as being at least 6 weeks postsurgical bilateral oophorectomy with or without hysterectomy (confirmed by operative note if without hysterectomy), or as having at least 12 continuous months of spontaneous amenorrhea, or as having at least 6 continuous months of spontaneous amenorrhea confirmed by a serum follicle-stimulating hormone concentration >40 mIU/mL and a negative pregnancy test. Subjects were required to have normal laboratory parameters (or acceptable deviations noted as not clinically significant by the investigator) at study entry and thus no biochemical evidence of abnormal renal or hepatic function.

Exclusion criteria included Paget's disease, parathyroid disease, thyroid disease, fracture of a long bone within 12 weeks of screening (all groups; based on medical history and a thyroid-stimulating hormone assessment at screening), current use of therapies for osteoporosis, or use of hormone-replacement therapy within the previous 12 months or BP during the previous 24 months (with the exception of the BP groups in the single-dose study). For cohorts 1 to 6 in the single-dose study and all subjects in the multiple-dose study, stable chronic conditions or chronic medications (other than antacids, histamine H2-receptor antagonists, and topical ophthalmic medications) were not permitted. For cohorts 7 and 8 in the single-dose study, subjects were required to be taking or recently discontinued (not more than 3 months before randomization) alendronate, having taken alendronate for at least 12 of the previous 18 months. These subjects were also permitted regular doses of antacids, antihypertensive agents, cholesterol-lowering agents, histamine H2-receptor antagonists, proton pump inhibitors, and topical ophthalmic medications. Subjects did not receive calcium or vitamin D supplements, unless it was part of their baseline drug therapy.

Study procedures

Blosozumab was supplied as lyophilized powder in glass vials, manufactured to deliver 25 mg (single-dose study) or 48 mg (multiple-dose study) blosozumab when reconstituted for administration according to pharmacy instructions. Placebo was 0.9% sodium chloride injection, United States Pharmacopeia. Blosozumab and/or placebo were administered as sc injection(s) and as an iv infusion across the two studies.

After the final study drug administration, all subjects were followed for 12 weeks for safety, PK, and PD assessments. All subjects had blood samples taken to measure antibodies against blosozumab using a validated screening modified enzyme-linked immunosorbent assay (ELISA) designed to perform in the presence of blosozumab; samples were taken at baseline (pre-dose day 1), day 29, and day 85, with an additional sample on day 141 in the multiple-dose study. The analysis was conducted at Pacific Biomarkers, Inc. (Seattle, WA, USA). Human serum samples obtained during both studies were analyzed at Prevalere Life Sciences, LLC (Whitesboro, NY, USA) for blosozumab concentrations using a validated ELISA method. BMD was measured by dual-energy X-ray absorptiometry (DXA) in multiple skeletal locations of the hip and lumbar spine, using either a Hologic Discovery (Hologic, Inc., Waltham, MA, USA), Hologic QDR-4500, or GE Lunar Prodigy (GE Lunar, Madison, WI, USA) densitometer. Serum concentrations of osteocalcin (OC) and N-terminal propeptide of type 1 procollagen (P1NP) were measured using a validated radioimmunoassay (OSTEO-RIACT kit (CIS US Inc., Bedford, MA), [LLQ 1.1 ng/mL; intra- and interassay coefficient of variation (CV) 2.82% and 5.6% to 13.0%, respectively] and Intact UniQ PINP RIA kit (Orion Diagnostica, Espoo, Finland), [LLQ 4.9 µg/L; intra- and interassay CV 2.6% to 3.2% and 6.0% to 10.0%, respectively], respectively), bone-specific alkaline phosphatase (BSAP) using a validated immunoenzymatic chemiluminescent assay (Beckman-Coulter Ostase assay on Beckman DxI 800 instrument (Beckman Coulter Inc., Brea, CA), [LLQ 0.1 µg/L; intra- and interassay CV 2.5% to 4.4% and 4.6% to 7.0%, respectively]), and C-terminal fragment of type 1 collagen (CTx) using a validated ELISA (Serum Crosslaps, IDS (formerly Nordic Bioscience Diagnostics), Herlev, Denmark, [intra- and interassay CV 4.9% to 6.4% and 9.5% to 10.1%, respectively]). These analyses were conducted at Covance Central Laboratory Services (CCLS; Indianapolis, IN, USA). Serum levels of total sclerostin were measured at Pacific Biomarkers, using a validated modified ELISA, designed to perform in the presence of blosozumab.

Statistical analyses

Bone mineral density and biomarker responses were analyzed using the full analysis set, which included data from all enrolled subjects who received study drug (blosozumab or placebo) according to the subject's assigned treatment. The effects of blosozumab on BMD and biomarker responses were evaluated using a mixed-effect model repeated measures analysis at the 0.05 significance level. Factors in the model included time, treatment, and the interaction of treatment by time. Least squares means and the 95% confidence limits for percent changes from baseline for each treatment group were computed. Safety analyses were conducted for all enrolled subjects, whether or not they completed all protocol requirements. Summary statistics, including N, mean, and standard deviation or standard error, where appropriate, were provided.

Results

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

Study population

In the single-dose study, 60 subjects entered the study and were randomized. Of these, 59 subjects completed the study; 1 subject discontinued after the day 28 procedures because of subject decision (personal reasons; no adverse events [AE] reported). In the multiple-dose study, 59 subjects entered the study and were randomized. Of these, 56 subjects completed all doses of study drug and 55 subjects completed the study per protocol; 1 subject was lost to follow-up after the day 85 procedures and 3 subjects withdrew or were withdrawn after the first dose of study drug (AE, n = 1 [750 mg blosozumab; vomiting]; physician decision, n = 1 [placebo; fractured foot on day 8]; subject decision, n = 1 [540 mg blosozumab; withdrew consent; no AEs reported]).

The demographics and baseline characteristics of each study population are summarized in Table 1. The mean age for the single-dose study and the multiple-dose study was 58 and 59 years, respectively. The majority of subjects in each study were white (single-dose study, 91.7%; multiple-dose study, 76.3%).

Table 1. Demographic and Baseline Characteristics
 Single-dose study n = 60Multiple-dose study n = 59
  1. BP = prior bisphosphonate exposure.

  2. Data are mean ± SD unless otherwise noted.

  3. a

    Lumbar spine regions L1 to L4.

  4. b

    Left hip.

Age (years)58 ± 659 ± 8
Weight (kg)68 ± 966 ± 12
Race, n (%)  
White55 (91.7)45 (76.3)
Black or African American3 (5.0)2 (3.4)
Asian1 (1.7)12 (20.3)
Native American1 (1.7)0 (0.0)
Body mass index (kg/m2)26 ± 326 ± 3
Lumbar spine T-scorea–1.3 ± 1.1 (all)–1.4 ± 1.2
 –2.0 ± 0.8 (BP; n = 12) 
Hip T-scoreb–0.6 ± 0.8 (all)–1.0 ± 0.9
 –0.9 ± 1.0 (BP; n = 12) 

Safety

Blosozumab was generally well tolerated after single or multiple administrations (up to 750 mg). No deaths occurred during either study. In the multiple-dose study, one serious adverse event (SAE) of moderate concussion after a car accident, which resulted in overnight hospitalization, was reported and was considered unrelated to the study drug by the investigator. The event occurred 27 days after the final infusion of the study drug (750 mg blosozumab). One subject withdrew because of an AE of vomiting, which occurred after the first dose of 750 mg blosozumab iv in the multiple-dose study.

The majority of AEs were mild. The most common (reported in ≥4 subjects) AEs (reported in ≥4 subjects) across the 2 studies, regardless of causality, were arthralgia, back pain, fatigue, headache, injection site reactions, nasal congestion, nausea, upper respiratory tract infection, and vomiting (Table 2 and Table 3 present the most common AEs for the single-dose and multiple-dose study, respectively). Injection site reactions were mild, localized, and self-limiting, and there was no trend for increasing severity of reactions with repeated doses of blosozumab.

Table 2. Adverse Event Summary for the Single-Dose Study
 No. of adverse events (no. of subjects) single-dose study n = 60
Bl 7.5 mg (n = 6)Bl 25 mg (n = 6)Bl 75 mg (n = 6)Bl 225 mg (n = 6)Bl 750 mg (n = 6)Bl 150 mg sc (n = 6)Bl 225 mg BP (n = 6)Bl 750 mg BP (n = 6)Placebo (n = 12)
  1. Bl = blosozumab; BP = prior bisphosphonate exposure; n = number of subjects studied; sc = subcutaneous.

Arthralgia1(1)1(1)    1(1)1(1) 
Back pain  1(1)1(1)1(1) 1(1)1(1)2(2)
Fatigue3(3)   1(1)    
Headache3(2)4(3)  1(1)1(1)3(3)1(1)1(1)
Nausea 1(1)  2(2) 1(1)  
Upper respiratory tract infection1(1)6(4) 4(3)1(1)1(1) 2(2)2(2)
Vomiting 1(1)    3(1)  
Table 3. Adverse Event Summary for the Multiple-Dose Study
 No. of adverse events (no. of subjects) multiple-dose study n = 59
Bl 180 mg sc Q4W (n = 9)Bl 270 mg sc Q4W (n = 10)Bl 270 mg sc Q2W (n = 11)Bl 540 mg iv Q4W (n = 9)Bl 750 mg iv Q2W (n = 8)Placebo sc & iv (n = 12)
  1. Bl = blosozumab; injection site reactions = discomfort, erythema, hemorrhage, inflammation, mass, pain, pruritus, rash, reaction, and warmth; iv = intravenous; n = number of subjects studied; Q2W = once every 2 weeks; Q4W = once every 4 weeks; sc = subcutaneous.

Arthralgia3(1)1(1)    
Back pain2(2)     
Fatigue1(1)  2(2)  
Headache1(1)8(4)2(2)1(1)1(1)7(5)
Injection site reactions3(3)11(5)16(9) 2(2)2(2)
Nasal congestion2(2) 1(1) 1(1) 
Nausea 1(1)1(1) 1(1)1(1)
Upper respiratory tract infection1(1)2(2)  2(2)3(3)
Vomiting1(1)3(2)  2(1)2(2)

During the course of the studies, there were no clinically significant alterations in hematology, clinical chemistry, vital signs, urinalysis, or electrocardiogram measurements.

In the multiple-dose study, there was a dose-related trend for increased mean intact parathyroid hormone (iPTH) at day 57 (iPTH not measured in the single-dose study); this trend was also apparent at day 4 for the 750-mg Q2W group. Mean iPTH levels were above the upper limit of normal for the 750-mg Q2W group from day 4 onward but trended upward within the normal range for the other dose groups. The increase in iPTH was associated with a dose-related reduction in mean urinary calcium levels, which was returning to baseline by day 113 for the lower doses but still reduced on day 113 for the 540-mg Q4W and 750-mg Q2W groups. There was no clinically significant impact on serum calcium levels, although there was a suggestion of a downward trend within the normal limits of the assay, despite the reduced urinary calcium levels. Scatter plots showing change from baseline in serum and urinary calcium levels, relative to iPTH, are provided as Supplemental Figs. S1 and S2, respectively.

Antibodies against blosozumab were detected after single (23% of subjects) and multiple administrations (36% of subjects) with low titers in general. In the single-dose study, titers ranged from 1:5 to 1:320 and the majority were 1:10 or 1:20. In the multiple-dose study, titers predominantly ranged from 1:5 to 1:40, with a single result each of 1:80 (180 mg Q4W; day 141) and 1:800 (270 mg Q2W; day 141). The numbers of subjects with positive titers are shown in Table 4. There was no evidence for neutralization based on drug exposure or PD data and no suggestion of any impact on safety profile associated with antibodies against blosozumab.

Table 4. Subjects With Positive Antiblosozumab Results
Blosozumab dose (mg)No. of subjects with positive antiblosozumab results
BaselineDay 29Day 85Day 141At least 1 positive result
  1. BP = prior bisphosphonate exposure; iv = intravenous; NA = not applicable; Q2W = once every 2 weeks; Q4W = once every 4 weeks; sc = subcutaneous.

7.5 iv000NA0
25 iv000NA0
75 iv001NA1
150 sc002NA2
225 iv024NA4
225 (BP) iv000NA0
750 iv001NA1
750 (BP) iv002NA2
180 Q4W sc01334
270 Q4W sc01424
270 Q2W sc00223
540 Q4W iv00011
750 Q2W iv10055

Bone mineral density

Fig. 2A shows the percent increase in lumbar spine (L1 to L4) BMD by group on day 85 for the single-dose study. After the single sc or iv dose of blosozumab, dose-dependent lumbar spine BMD increases were observed on day 85. Of note, the mean BMD increases were statistically different from baseline for BP (mean = 2.40%, p = 0.021) and naive subjects (mean = 3.41%, p = 0.002) after a 750-mg iv dose. No statistically significant difference was detected between these two groups of subjects (p = 0.820 for 225 mg, p = 0.554 for 750 mg), with the awareness that the present study was not powered to detect BMD differences.

image

Figure 2. Lumbar spine BMD percent change from baseline by dose group on day 85 for the single-dose (A) and 8-week multiple-dose (B) studies. Error bars are 95% confidence limits. BMD = bone mineral density; BP = prior bisphosphonate exposure; iv = intravenous; Q2W = once every 2 weeks; Q4W = once every 4 weeks; sc = subcutaneous.

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Fig. 2B shows the percent increase in lumbar spine (L1 to L4) BMD by group on day 85 for the multiple-dose study. Across the 5 blosozumab dosing regimens tested, the mean percent increase of total lumbar spine BMD from baseline was between 2.52% (180 mg sc Q4W) and 7.71% (750 mg iv Q2W) measured on day 85, and generally showed a dose-dependent pattern. Of note, the mean BMD change for the 540-mg iv Q4W dosing group (4.83%) was less than that for the 270-mg sc Q2W (5.61%) dosing group, although the total monthly exposure to blosozumab was lower in the latter group because of the bioavailability associated with sc administration (the monthly area under the concentration versus time curve of 270 mg sc Q2W was approximately 50% of 540 mg iv Q4W post the last dose). Compared with placebo, statistically significant increases in lumbar spine BMD were observed in the 540-mg iv Q4W (p = 0.003), 270-mg sc Q2W (p < 0.001), and 750-mg iv Q2W (p < 0.001) blosozumab dosing groups.

Total hip BMD was also measured in the single- and multiple-dose studies. The mean total hip BMD percent change from baseline on day 85 after blosozumab administration ranged from –2.9% to 2.4% in the single-dose study, and from –0.8% to 1.7% in the multiple-dose study. The increases were not statistically significant from placebo in either study (all p values were greater than 0.05).

Biomarker responses

After blosozumab administration at all dose levels investigated, there were dose-dependent increases in serum levels of total sclerostin (Fig. 3). Although the assay detects both free sclerostin and blosozumab-bound sclerostin, the decline of the total sclerostin profiles was always in parallel to the decline of the blosozumab concentration profiles (data on file), implying blosozumab-bound sclerostin was the predominant component measured. Therefore, the dose-dependent elevation of total sclerostin indicates the target engagement of blosozumab. Of note, the baseline sclerostin values among subjects were variable (Fig. 3A, B). As a result, the percentage change of sclerostin levels from baseline did not follow the rank order of dose levels and dosing frequencies (Fig. 3C, D). However, in the multiple-dose study, it is clear that the sclerostin levels fluctuated less during the dosing period and remained above baseline for a longer period after the last dose of blosozumab with higher and more frequent dosing regimens, suggesting that higher, frequent doses better maintain sclerostin neutralization.

image

Figure 3. Serum levels of total sclerostin (A, B) and percent change from baseline (C, D) post single-dose or 8-week repeated doses of blosozumab, respectively. Data are mean and standard error. BP = prior bisphosphonate exposure; iv = intravenous; Q2W = once every 2 weeks; Q4W = once every 4 weeks; sc = subcutaneous.

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Dose-dependent biomarker responses were also observed in OC (Fig. 4A, B), BSAP (Fig. 4C, D), and P1NP (Fig. 4E, F). The biomarker changes seen post-dose in both the single- and multiple-dose studies were statistically significant at multiple-dose levels and time points and a clear dose-response relationship was detected. In the multiple-dose study, the magnitude of the P1NP response appears to be reduced with successive doses of blosozumab (Fig. 4F). After a single sc or iv dose of blosozumab, CTx levels decreased by approximately 30% to 50%, in a relatively dose-dependent manner, then gradually returned to baseline (Fig. 4G). With repeated doses, CTx gradually returned to baseline, which was not obviously dose-dependent (Fig. 4H). The only exception was 750 mg iv Q2W, where the CTx level stayed depressed for a longer period of time during the treatment, and a clear rebound effect after the last dose (with mean of approximately 100% increase from baseline) was observed.

image

Figure 4. Responses of bone biochemical markers in serum post single-dose (left panels) or 8-week repeated doses (right panels) of blosozumab in BP naive postmenopausal women. Plots show means and standard errors of percent change from baseline. BSAP = bone-specific alkaline phosphatase; CTx = C-terminal fragment of type 1 collagen; iv = intravenous; OC = osteocalcin; PN1P = N-terminal propeptide of type 1 procollagen; Q2W = once every 2 weeks; Q4W = once every 4 weeks; sc = subcutaneous.

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Compared with naive subjects, the baseline sclerostin levels in subjects with prior BP exposure were similar, whereas the sclerostin concentration change from baseline appears to be higher and more sustainable in the prior BP cohorts at both dose levels tested (Fig. 3A, C). The baseline P1NP and CTx levels in subjects with prior BP exposure were evidently lower, consistent with the mechanism of action for BP, that is, to reduce the bone resorption activity and the overall bone turnover rate.[11] Although dose-dependent bone biomarker responses were also observed in prior BP subjects (Fig. 5), the magnitude of the response was slightly lower based on absolute change from baseline for P1NP and CTx (Fig. 5B, D), as well as percent change from baseline for CTx (Fig. 5C) at both dose levels tested. Because of the lower baseline values, the P1NP responses presented as percent change from baseline are higher in prior BP subjects.

image

Figure 5. Comparison of single-dose blosozumab effects on serum levels of N-terminal propeptide of type 1 procollagen (A, B) and C-terminal fragment of type 1 collagen (C, D) in BP naive postmenopausal women and those with prior BP exposure. BP = prior bisphosphonate exposure; CTx = C-terminal fragment of type 1 collagen; iv = intravenous; PN1P = N-terminal propeptide of type 1 procollagen.

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Discussion

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

This article describes the first clinical evaluation of single and multiple administrations of blosozumab to postmenopausal women. Blosozumab was generally well tolerated and demonstrated an overall favorable safety profile. A single SAE of concussion was reported approximately 1 month after the final dose of blosozumab 750 mg in the multiple-dose study and was considered unrelated to the study drug. There were no deaths, and the majority of AEs reported were of mild intensity. The only AE leading to withdrawal was an episode of vomiting after the first dose of 750 mg blosozumab in the multiple-dose study. Antibodies to blosozumab were detected in some subjects after single and multiple administrations, but the majority were with low titers. The rationale for exploring the generation of antibodies to a therapeutic protein is to understand any clinical implications of such antibodies rather than providing frequency and titer data, which can be misleading if used for comparison to data on other therapeutic proteins using different assays. Based on the data generated from these two studies, there was no evidence of a link between antiblosozumab antibody generation and differences in safety, PK, or PD data, ie, there are no apparent clinical consequences of the antiblosozumab antibodies from the available data. Blosozumab exhibited anabolic effects on bone, as demonstrated through bone biomarkers and BMD. Although only 12 subjects with prior BP exposure received a single iv dose of blosozumab, in an uncontrolled setting, there did not seem to be a clear impact of prior BP therapy on the effects of blosozumab when considering the bone biomarker and BMD responses seen.

The changes in calcium and iPTH observed during the multiple-dose study are likely a physiological consequence of the mechanism of action for blosozumab (ie, increased bone formation placing a demand on calcium reserves) and were not considered clinically significant. The changes were mostly within the normal range for the assay for iPTH, and serum calcium levels were preserved within the normal range but trended downward, returning toward baseline after stopping blosozumab. These parameters should be explored further in future studies of blosozumab.

Blosozumab dose-dependent PD responses were observed in various biomarkers, including sclerostin, P1NP, CTx, BSAP, OC, and lumbar spine BMD. These changes suggest that blosozumab effectively neutralized the target (sclerostin), resulting in increased bone anabolic activities (P1NP, BSAP, OC) and decreased bone resorption activities (CTx), leading to an increase in lumbar spine BMD. The BMD responses for the 270-mg sc Q2W and 540-mg iv Q4W regimens were the reverse of expectation, with the 270-mg Q2W sc showing a larger effect, despite the lower drug exposure associated with sc administration. This could be a reflection of the dosing regimen and/or the small sample size. The P1NP data suggest a hint of tolerance, reflected in the decreased magnitude of P1NP response over time with repeated doses of blosozumab. This effect appears to be independent of the generation of antiblosozumab antibodies and will be explored further in longer-duration studies of blosozumab.

Historical data suggest that the effect of teriparatide, a marketed bone anabolic agent, on bone biomarkers and BMD is blunted in subjects who have previously been exposed to BP.[12] Although a blunting of the PD effect with blosozumab was not anticipated, many of the target osteoporotic population would have received a BP previously, so prior BP use was evaluated as an open-label addition to the single-dose study. Compared with naive subjects, sclerostin concentration change from baseline appeared higher and more sustainable in the BP cohorts. Although dose-dependent responses for P1NP, CTx (absolute change), and lumbar spine BMD were also observed in BP subjects, the magnitude of these responses were slightly lower than those in naive subjects. However, given the small number of subjects enrolled in the single-dose study and highly variable PD responses, it is premature to conclude whether blunting effects exist in BP subjects.

Antiblosozumab antibodies were detected during at least one time point in 11 of the 48 subjects (23%) in the single-dose study and in 17 of the 47 subjects (36%) in the multiple-dose study. The majority of the titers were low (up to 1:40), and there was no suggestion of a link between antiblosozumab antibody generation and differences in safety, drug exposure, or PD data. Collectively, these data do not raise any concerns regarding immunogenic potential of blosozumab but support continued evaluation of antiblosozumab antibodies in subsequent clinical studies.

The publication of Padhi and colleagues[9] describes the single-dose data generated with another antisclerostin antibody, AMG 785 (romosozumab). Although the design and conduct of that study is not directly comparable to the single-dose blosozumab study described in this article, the PD data (BMD and bone biomarkers) described by Padhi and colleagues also show a dose response and are generally consistent with the single-dose data presented here for blosozumab.

In summary, blosozumab was well tolerated and exhibited anabolic effects on bone in both studies. These results support further clinical investigation of blosozumab as a potential anabolic therapy for osteoporosis.

Disclosures

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

This study was funded by Eli Lilly and Company. All authors are employees and stockholders of Eli Lilly and Company.

Acknowledgments

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

The authors thank and acknowledge Jessie Bishop, MPH, of Eli Lilly & Co., and Michelle Carey, PhD, of PharmaNet/i3, for assistance with the preparation of this article. The authors also thank the investigators and site staff at Covance and Lilly Clinical Research Units. The studies were funded by Eli Lilly & Co.

Authors' roles: Study design: JMC, TW, LH, CCT, and AYC. Study conduct: JMC, TW, LH, CCT, and AYC. Data collection: JMC, TW, LH, CCT, and AYC. Data analysis: LH, CCT, and AYC. Data interpretation: JMC, TW, LH, CCT, and AYC. Drafting manuscript: JMC, TW, LH, CCT, and AYC. Revising manuscript content: JMC, TW, LH, CCT, and AYC. Approving final version of manuscript: JMC, TW, LH, CCT, and AYC. LH, CCT, and AYC take responsibility for the integrity of the data analysis.

References

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

Supporting Information

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Materials and Methods
  5. Results
  6. Discussion
  7. Disclosures
  8. Acknowledgments
  9. References
  10. Supporting Information

Additional Supporting Information may be found in the online version of this article.

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jbmr2092-sm-0001-SuppFig-S1.pdf115KSupp Fig. S1
jbmr2092-sm-0002-SuppFig-S2.pdf106KSupp Fig. S2

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