Pharmacotherapeutic group: Drugs for treatment of bone diseases – Other drugs affecting bone structure and mineralisation. ATC code: M05BX04
Bildyos is a biosimilar medicinal product. Detailed information is available on the MHRA website.
Mechanism of action
Denosumab is a fully human monoclonal antibody (IgG2) that targets and binds with high affinity and specificity to RANKL, preventing activation of its receptor, RANK, on the surface of osteoclast precursors and osteoclasts. Prevention of the RANKL/RANK interaction inhibits osteoclast formation, function and survival, thereby decreasing bone resorption in cortical and trabecular bone.
Pharmacodynamic effects
Denosumab treatment rapidly reduced the rate of bone turnover, reaching a nadir for the bone resorption marker serum type 1 C-telopeptides (CTX) (85% reduction) by 3 days, with reductions maintained over the dosing interval. At the end of each dosing interval, CTX reductions were partially attenuated from maximal reduction of ≥ 87% to approximately ≥ 45% (range 45–80%), reflecting the reversibility of denosumab's effects on bone remodelling once serum levels diminish. These effects were sustained with continued treatment. Bone turnover markers generally reached pre-treatment levels within 9 months after the last dose. Upon re-initiation, reductions in CTX by denosumab were similar to those observed in patients initiating primary denosumab treatment.
Immunogenicity
Anti-denosumab antibodies may develop during denosumab treatment. No apparent correlation of antibody development with pharmacokinetics, clinical response or adverse event has been observed.
Clinical efficacy and safety in postmenopausal women with osteoporosis
Efficacy and safety of denosumab administered once every 6 months for 3 years were investigated in postmenopausal women (7 808 women aged 60-91 years, of which 23.6% had prevalent vertebral fractures) with baseline bone mineral density (BMD) T-scores at the lumbar spine or total hip between –2.5 and –4.0 and a mean absolute 10-year fracture probability of 18.60% (deciles: 7.9–32.4%) for major osteoporotic fracture and 7.22% (deciles: 1.4–14.9%) for hip fracture. Women with other diseases or on therapies that may affect bone were excluded from this study. Women received calcium (at least 1 000 mg) and vitamin D (at least 400 IU) supplementation daily.
Effect on vertebral fractures
Denosumab significantly reduced the risk of new vertebral fractures at 1, 2 and 3 years (p < 0.0001) (see table 2).
Table 2 The effect of denosumab on the risk of new vertebral fractures
| | Proportion of women with fracture (%) | Absolute risk reduction (%) (95% CI) | Relative risk reduction (%) (95% CI) |
| Placebo n = 3 906 | Denosumab n = 3 902 |
| 0-1 year | 2.2 | 0.9 | 1.4 (0.8, 1.9) | 61 (42, 74)** |
| 0-2 years | 5.0 | 1.4 | 3.5 (2.7, 4.3) | 71 (61, 79)** |
| 0-3 years | 7.2 | 2.3 | 4.8 (3.9, 5.8) | 68 (59, 74)* |
*p < 0.0001, **p < 0.0001 – exploratory analysis
Effect on hip fractures
Denosumab demonstrated a 40% relative reduction (0.5% absolute risk reduction) in the risk of hip fracture over 3 years (p < 0.05). The incidence of hip fracture was 1.2% in the placebo group compared to 0.7% in the denosumab group at 3 years.
In a post-hoc analysis in women > 75 years, a 62% relative risk reduction was observed with denosumab (1.4% absolute risk reduction, p < 0.01).
Effect on all clinical fractures
Denosumab significantly reduced fractures across all fracture types/groups (see table 3).
Table 3 The effect of denosumab on the risk of clinical fractures over 3 years
| | Proportion of women with fracture (%)+ | Absolute risk reduction (%) (95% CI) | Relative risk reduction (%) (95% CI) |
| Placebo n = 3 906 | Denosumab n = 3 902 |
| Any clinical fracture1 | 10.2 | 7.2 | 2.9 (1.6, 4.2) | 30 (19, 41)*** |
| Clinical vertebral fracture | 2.6 | 0.8 | 1.8 (1.2, 2.4) | 69 (53, 80)*** |
| Non-vertebral fracture2 | 8.0 | 6.5 | 1.5 (0.3, 2.7) | 20 (5, 33)** |
| Major non-vertebral fracture3 | 6.4 | 5.2 | 1.2 (0.1, 2.2) | 20 (3, 34)* |
| Major osteoporotic fracture4 | 8.0 | 5.3 | 2.7 (1.6, 3.9) | 35 (22, 45)*** |
*p ≤ 0.05, **p = 0.0106 (secondary endpoint included in multiplicity adjustment), ***p ≤ 0.0001
+ Event rates based on Kaplan-Meier estimates at 3 years.
1 Includes clinical vertebral fractures and non-vertebral fractures.
2 Excludes those of the vertebrae, skull, facial, mandible, metacarpus, and finger and toe phalanges.
3 Includes pelvis, distal femur, proximal tibia, ribs, proximal humerus, forearm, and hip.
4 Includes clinical vertebral, hip, forearm, and humerus fractures, as defined by the WHO.
In women with baseline femoral neck BMD ≤ -2.5, denosumab reduced the risk of non-vertebral fracture (35% relative risk reduction, 4.1% absolute risk reduction, p < 0.001, exploratory analysis).
The reduction in the incidence of new vertebral fractures, hip fractures and non-vertebral fractures by denosumab over 3 years were consistent regardless of the 10-year baseline fracture risk.
Effect on bone mineral density
Denosumab significantly increased BMD at all clinical sites measured, versus placebo at 1, 2 and 3 years. Denosumab increased BMD by 9.2% at the lumbar spine, 6.0% at the total hip, 4.8% at the femoral neck, 7.9% at the hip trochanter, 3.5% at the distal 1/3 radius and 4.1% at the total body over 3 years (all p < 0.0001).
In clinical studies examining the effects of discontinuation of denosumab, BMD returned to approximately pre-treatment levels and remained above placebo within 18 months of the last dose. These data indicate that continued treatment with denosumab is required to maintain the effect of the medicinal product. Re-initiation of denosumab resulted in gains in BMD similar to those when denosumab was first administered.
Open-label extension study in the treatment of postmenopausal osteoporosis
A total of 4 550 women (2 343 denosumab and 2 207 placebo) who missed no more than one dose of investigational product in the pivotal study described above and completed the month 36 study visit agreed to enrol in a 7-year, multinational, multicentre, open-label, single-arm extension study to evaluate the long-term safety and efficacy of denosumab. All women in the extension study were to receive denosumab 60 mg every 6 months, as well as daily calcium (at least 1 g) and vitamin D (at least 400 IU). A total of 2 626 subjects (58% of the women included in the extension study i.e. 34% of the women included in the pivotal study) completed the extension study.
In patients treated with denosumab for up to 10 years, BMD increased from the pivotal study baseline by 21.7% at the lumbar spine, 9.2% at the total hip, 9.0% at the femoral neck, 13.0% at the trochanter and 2.8% at the distal 1/3 radius. The mean lumbar spine BMD T-score at the end of the study was −1.3 in patients treated for 10 years.
Fracture incidence was evaluated as a safety endpoint but efficacy in fracture prevention cannot be estimated due to high number of discontinuations and open-label design. The cumulative incidence of new vertebral and non-vertebral fractures were approximately 6.8% and 13.1% respectively, in patients who remained on denosumab treatment for 10 years (n = 1 278). Patients who did not complete the study for any reason had higher on-treatment fracture rates.
Thirteen adjudicated cases of osteonecrosis of the jaw (ONJ) and two adjudicated cases of atypical fractures of the femur occurred during the extension study.
Clinical efficacy and safety in men with osteoporosis
Efficacy and safety of denosumab once every 6 months for 1 year were investigated in 242 men aged 31–84 years. Subjects with an eGFR < 30 mL/min/1.73 m2 were excluded from the study. All men received calcium (at least 1 000 mg) and vitamin D (at least 800 IU) supplementation daily.
The primary efficacy variable was percent change in lumbar spine BMD, fracture efficacy was not evaluated. Denosumab significantly increased BMD at all clinical sites measured, relative to placebo at 12 months: 4.8% at lumbar spine, 2.0% at total hip, 2.2% at femoral neck, 2.3% at hip trochanter, and 0.9% at distal 1/3 radius (all p < 0.05). Denosumab increased lumbar spine BMD from baseline in 94.7% of men at 1 year. Significant increases in BMD at lumbar spine, total hip, femoral neck and hip trochanter were observed by 6 months (p < 0.0001).
Bone histology in postmenopausal women and men with osteoporosis
Bone histology was evaluated in 62 postmenopausal women with osteoporosis or with low bone mass who were either naïve to osteoporosis therapies or had transitioned from previous alendronate therapy following 1–3 years treatment with denosumab. Fifty-nine women participated in the bone biopsy sub-study at month 24 (n = 41) and/or month 84 (n = 22) of the extension study in postmenopausal women with osteoporosis. Bone histology was also evaluated in 17 men with osteoporosis following 1 year treatment with denosumab. Bone biopsy results showed bone of normal architecture and quality with no evidence of mineralisation defects, woven bone or marrow fibrosis. Histomorphometry findings in the extension study in postmenopausal women with osteoporosis showed that the antiresorptive effects of denosumab, as measured by activation frequency and bone formation rates, were maintained over time.
Clinical efficacy and safety in patients with bone loss associated with androgen deprivation
Efficacy and safety of denosumab once every 6 months for 3 years were investigated in men with histologically confirmed non-metastatic prostate cancer receiving ADT (1 468 men aged 48–97 years) who were at increased risk of fracture (defined as > 70 years, or < 70 years with a BMD T-score at the lumbar spine, total hip, or femoral neck < -1.0 or a history of an osteoporotic fracture). All men received calcium (at least 1 000 mg) and vitamin D (at least 400 IU) supplementation daily.
Denosumab significantly increased BMD at all clinical sites measured, relative to treatment with placebo at 3 years: 7.9% at the lumbar spine, 5.7% at the total hip, 4.9% at the femoral neck, 6.9% at the hip trochanter, 6.9% at the distal 1/3 radius and 4.7% at the total body (all p < 0.0001). In a prospectively planned exploratory analysis, significant increases in BMD were observed at the lumbar spine, total hip, femoral neck and the hip trochanter 1 month after the initial dose.
Denosumab demonstrated a significant relative risk reduction of new vertebral fractures: 85% (1.6% absolute risk reduction) at 1 year, 69% (2.2% absolute risk reduction) at 2 years and 62% (2.4% absolute risk reduction) at 3 years (all p < 0.01).
Clinical efficacy and safety in patients with bone loss associated with adjuvant aromatase inhibitor therapy
Efficacy and safety of denosumab once every 6 months for 2 years were investigated in women with non-metastatic breast cancer (252 women aged 35–84 years) and baseline BMD T-scores between -1.0 to -2.5 at the lumbar spine, total hip or femoral neck. All women received calcium (at least 1 000 mg) and vitamin D (at least 400 IU) supplementation daily.
The primary efficacy variable was percent change in lumbar spine BMD, fracture efficacy was not evaluated. Denosumab significantly increased BMD at all clinical sites measured, relative to treatment with placebo at 2 years: 7.6% at lumbar spine, 4.7% at total hip, 3.6% at femoral neck, 5.9% at hip trochanter, 6.1% at distal 1/3 radius and 4.2% at total body (all p < 0.0001).
Treatment of bone loss associated with systemic glucocorticoid therapy
Efficacy and safety of denosumab were investigated in 795 patients (70% women and 30% men) aged 20 to 94 years treated with ≥ 7.5 mg daily oral prednisone (or equivalent).
Two subpopulations were studied: glucocorticoid-continuing (≥ 7.5 mg daily prednisone or its equivalent for ≥ 3 months prior to study enrolment; n = 505) and glucocorticoid-initiating (≥ 7.5 mg daily prednisone or its equivalent for < 3 months prior to study enrolment; n = 290). Patients were randomised (1:1) to receive either denosumab 60 mg subcutaneously once every 6 months or oral risedronate 5 mg once daily (active control) for 2 years. Patients received calcium (at least 1 000 mg) and vitamin D (at least 800 IU) supplementation daily.
Effect on Bone Mineral Density (BMD)
In the glucocorticoid-continuing subpopulation, denosumab demonstrated a greater increase in lumbar spine BMD compared to risedronate at 1 year (denosumab 3.6%, risedronate 2.0%; p < 0.001) and 2 years (denosumab 4.5%, risedronate 2.2%; p < 0.001). In the glucocorticoid-initiating subpopulation, denosumab demonstrated a greater increase in lumbar spine BMD compared to risedronate at 1 year (denosumab 3.1%, risedronate 0.8%; p < 0.001) and 2 years (denosumab 4.6%, risedronate 1.5%; p < 0.001).
In addition, denosumab demonstrated a significantly greater mean percent increase in BMD from baseline compared to risedronate at the total hip, femoral neck, and hip trochanter.
The study was not powered to show a difference in fractures. At 1 year, the subject incidence of new radiological vertebral fracture was 2.7% (denosumab) versus 3.2% (risedronate). The subject incidence of non-vertebral fracture was 4.3% (denosumab) versus 2.5% (risedronate). At 2 years, the corresponding numbers were 4.1% versus 5.8% for new radiological vertebral fractures and 5.3% versus 3.8% for non-vertebral fractures. Most of the fractures occurred in the GC-C subpopulation.
Paediatric population
A single-arm phase III study evaluated the efficacy, safety, and pharmacokinetics was conducted in children with osteogenesis imperfecta, aged 2 to 17 years, 52.3% male, 88.2% Caucasian. A total of 153 subjects initially received subcutaneous (SC) denosumab 1 mg/kg, up to a maximum of 60 mg, every 6 months for 36 months. Sixty subjects transitioned to every 3 months dosing.
At month 12 of every 3 months dosing, the least squares (LS) mean (standard error, SE) change from baseline in lumbar spine BMD Z-score was 1.01 (0.12).
The most common adverse events reported during every 6 months dosing were arthralgia (45.8%), pain in extremity (37.9%), back pain (32.7%), and hypercalciuria (32.0%). Hypercalcaemia was reported during every 6 months (19%) and every 3 months (36.7%) dosing. Serious adverse events of hypercalcaemia (13.3%) were reported during every 3 months dosing.
In an extension study (N = 75), serious adverse events of hypercalcaemia (18.5%) were observed during every 3 months dosing.
The studies were terminated early due to the occurrence of life-threatening events and hospitalisations due to hypercalcaemia (see section 4.2).
In one multicentre, randomised, double-blind, placebo-controlled, parallel-group study conducted in 24 paediatric patients with glucocorticoid-induced osteoporosis, aged 5 to 17 years, evaluating change from baseline in lumbar spine BMD Z-score, safety and effectiveness were not established hence denosumab should not be used for this indication.
The licensing authority has waived the obligation to submit the results of studies with denosumab in all subsets of the paediatric population in the treatment of bone loss associated with sex hormone ablative therapy, and in subsets of the paediatric population below the age of 2 in the treatment of osteoporosis. See section 4.2 for information on paediatric use.