Pharmacotherapeutic group: Drugs for treatment of bone diseases – Other drugs affecting bone structure and mineralisation, ATC code: M05BX04
Enwylma is a biosimilar medicinal product. Detailed information is available on the MHRA website.
Mechanism of action
RANKL exists as a transmembrane or soluble protein. RANKL is essential for the formation, function and survival of osteoclasts, the sole cell type responsible for bone resorption. Increased osteoclast activity, stimulated by RANKL, is a key mediator of bone destruction in metastatic bone disease and multiple myeloma. Denosumab is a human monoclonal antibody (IgG2) that targets and binds with high affinity and specificity to RANKL, preventing the RANKL/RANK interaction from occurring and resulting in reduced osteoclast numbers and function, thereby decreasing bone resorption and cancer-induced bone destruction.
Giant cell tumours of bone are characterised by neoplastic stromal cells expressing RANK ligand and osteoclast-like giant cells expressing RANK. In patients with giant cell tumour of bone, denosumab binds to RANK ligand, significantly reducing or eliminating osteoclast-like giant cells. Consequently, osteolysis is reduced and proliferative tumour stroma is replaced with non-proliferative, differentiated, densely woven new bone.
Pharmacodynamic effects
In phase II clinical studies of patients with advanced malignancies involving bone, subcutaneous (SC) dosing of denosumab administered either every 4 weeks (Q4W) or every 12 weeks resulted in a rapid reduction in markers of bone resorption (uNTx/Cr, serum CTx), with median reductions of approximately 80% for uNTx/Cr occurring within 1 week regardless of prior bisphosphonate therapy or baseline uNTx/Cr level. In phase III clinical trials of patients with advanced malignancies involving bone, median uNTx/Cr reductions of approximately 80% were maintained through 49 weeks of denosumab treatment (120 mg every Q4W).
Immunogenicity
In clinical studies, neutralising antibodies have not been observed for denosumab in advanced cancer patients or giant cell tumour of bone patients. Using a sensitive immunoassay < 1% of patients treated with denosumab for up to 3 years tested positive for non-neutralising binding antibodies with no evidence of altered pharmacokinetics, toxicity, or clinical response.
Clinical efficacy and safety in patients with bone metastases from solid tumours
Efficacy and safety of 120 mg denosumab SC every 4 weeks or 4 mg zoledronic acid (dose-adjusted for reduced renal function) IV every 4 weeks were compared in three randomised, double-blind, active-controlled studies, in IV-bisphosphonate naïve patients with advanced malignancies involving bone: adults with breast cancer (study 1), other solid tumours or multiple myeloma (study 2), and castrate-resistant prostate cancer (study 3). Within these active-controlled clinical trials, safety was evaluated in 5,931 patients. Patients with prior history of ONJ or osteomyelitis of the jaw, an active dental or jaw condition requiring oral surgery, non-healed dental/oral surgery, or any planned invasive dental procedure, were not eligible for inclusion in these studies. The primary and secondary endpoints evaluated the occurrence of one or more skeletal related events (SREs). In studies demonstrating superiority of denosumab to zoledronic acid, patients were offered open-label denosumab in a pre-specified 2-year extension treatment phase. An SRE was defined as any of the following: pathologic fracture (vertebral or non-vertebral), radiation therapy to bone (including the use of radioisotopes), surgery to bone, or spinal cord compression.
Denosumab reduced the risk of developing a SRE, and developing multiple SREs (first and subsequent) in patients with bone metastases from solid tumours (see table 2).
Table 2. Efficacy results in patients with advanced malignancies involving bone
| | Study 1 breast cancer | Study 2 other solid tumours** or multiple myeloma | Study 3 prostate cancer | Combined advanced cancer |
| | denosumab | zoledronic acid | denosumab | zoledronic acid | denosumab | zoledronic acid | denosumab | zoledronic acid |
| N | 1,026 | 1,020 | 886 | 890 | 950 | 951 | 2,862 | 2,861 |
| First SRE |
| Median time (months) | NR | 26.4 | 20.6 | 16.3 | 20.7 | 17.1 | 27.6 | 19.4 |
| Difference in median time (months) | NA | 4.2 | 3.5 | 8.2 |
| HR (95% CI) / RRR (%) | 0.82 (0.71, 0.95) / 18 | 0.84 (0.71, 0.98) / 16 | 0.82 (0.71, 0.95) / 18 | 0.83 (0.76, 0.90) / 17 |
| Non-inferiority / Superiority p-values | < 0.0001† / 0.0101† | 0.0007† / 0.0619† | 0.0002† / 0.0085† | < 0.0001 / < 0.0001 |
| Proportion of patients (%) | 30.7 | 36.5 | 31.4 | 36.3 | 35.9 | 40.6 | 32.6 | 37.8 |
| First and subsequent SRE* |
| Mean number/ patient | 0.46 | 0.60 | 0.44 | 0.49 | 0.52 | 0.61 | 0.48 | 0.57 |
| Rate ratio (95% CI) / RRR (%) | 0.77 (0.66, 0.89) / 23 | 0.90 (0.77, 1.04) / 10 | 0.82 (0.71, 0.94) / 18 | 0.82 (0.75, 0.89) / 18 |
| Superiority p-value | 0.0012† | 0.1447† | 0.0085† | < 0.0001 |
| SMR per Year | 0.45 | 0.58 | 0.86 | 1.04 | 0.79 | 0.83 | 0.69 | 0.81 |
| First SRE or HCM |
| Median time (months) | NR | 25.2 | 19.0 | 14.4 | 20.3 | 17.1 | 26.6 | 19.4 |
| HR (95% CI) / RRR (%) | 0.82 (0.70, 0.95) / 18 | 0.83 (0.71, 0.97) / 17 | 0.83 (0.72, 0.96) / 17 | 0.83 (0.76, 0.90) / 17 |
| Superiority p-value | 0.0074 | 0.0215 | 0.0134 | < 0.0001 |
| First radiation to bone |
| Median time (months) | NR | NR | NR | NR | NR | 28.6 | NR | 33.2 |
| HR (95% CI) / RRR (%) | 0.74 (0.59, 0.94) / 26 | 0.78 (0.63, 0.97) / 22 | 0.78 (0.66, 0.94) / 22 | 0.77 (0.69, 0.87) / 23 |
| Superiority p-value | 0.0121 | 0.0256 | 0.0071 | < 0.0001 |
NR = not reached; NA = not available; HCM = hypercalcaemia of malignancy; SMR = skeletal morbidity rate; HR = Hazard Ratio; RRR = Relative Risk Reduction †Adjusted p-values are presented for studies 1, 2 and 3 (first SRE and first and subsequent SRE endpoints); *Accounts for all skeletal events over time; only events occurring ≥ 21 days after the previous event are counted.
** Including NSCLC, renal cell cancer, colorectal cancer, small cell lung cancer, bladder cancer, head and neck cancer, GI/genitourinary cancer and others, excluding breast and prostate cancer.
Figure 1. Kaplan-Meier plots of time to first on-study SRE
Dmab = Denosumab 120 mg Q4W
ZA = Zolendronic Acid 4 mg Q4W
N = Number of subjects randomised
*= Statistically significant for superiority; **= Statistically significant for non-inferiority
Disease progression and overall survival with bone metastases from solid tumours
Disease progression was similar between denosumab and zoledronic acid in all three studies and in the pre-specified analysis of all three studies combined.
In studies 1, 2 and 3, overall survival was balanced between denosumab and zoledronic acid in patients with advanced malignancies involving bone: patients with breast cancer (hazard ratio and 95% CI was 0.95 [0.81, 1.11]), patients with prostate cancer (hazard ratio and 95% CI was 1.03 [0.91, 1.17]), and patients with other solid tumours or multiple myeloma (hazard ratio and 95% CI was 0.95 [0.83, 1.08]). A post-hoc analysis in study 2 (patients with other solid tumours or multiple myeloma) examined overall survival for the 3 tumour types used for stratification (non-small cell lung cancer, multiple myeloma, and other). Overall survival was longer for denosumab in non-small cell lung cancer (hazard ratio [95% CI] of 0.79 [0.65, 0.95]; n = 702) and longer for zoledronic acid in multiple myeloma (hazard ratio [95% CI] of 2.26 [1.13, 4.50]; n = 180) and similar between denosumab and zoledronic acid in other tumour types (hazard ratio [95% CI] of 1.08 (0.90, 1.30); n = 894). This study did not control for prognostic factors and anti-neoplastic treatments. In a combined pre-specified analysis from studies 1, 2 and 3, overall survival was similar between denosumab and zoledronic acid (hazard ratio and 95% CI 0.99 [0.91, 1.07]).
Effect on pain
The time to pain improvement (i.e. ≥ 2-point decrease from baseline in BPI-SF worst pain score) was similar for denosumab and zoledronic acid in each study and the integrated analyses. In a post-hoc analysis of the combined dataset, the median time to worsening pain (> 4-point worst pain score) in patients with mild or no pain at baseline was delayed for denosumab compared to zoledronic acid (198 versus 143 days) (p = 0.0002).
Clinical efficacy in patients with multiple myeloma
Denosumab was evaluated in an international, randomised (1:1), double-blind, active-controlled study comparing denosumab with zoledronic acid in patients with newly diagnosed multiple myeloma, study 4.
In this study, 1,718 multiple myeloma patients with at least one bone lesion were randomised to receive 120 mg denosumab subcutaneously every 4 weeks (Q4W) or 4 mg zoledronic acid intravenously (IV) every 4 weeks (dose-adjusted for renal function). The primary outcome measure was demonstration of non-inferiority of time to first on study skeletal related event (SRE) as compared to zoledronic acid. Secondary outcome measures included superiority of time to first SRE, superiority of time to first and subsequent SRE, and overall survival. An SRE was defined as any of the following: pathologic fracture (vertebral or non-vertebral), radiation therapy to bone (including the use of radioisotopes), surgery to bone, or spinal cord compression.
Across both study arms, 54.5% of patients intended to undergo autologous PBSC transplantation, 95.8% patients utilised/planned to utilise a novel anti-myeloma agent (novel therapies include bortezomib, lenalidomide, or thalidomide) in first-line therapy, and 60.7% of patients had a previous SRE. The number of patients across both study arms with ISS stage I, stage II, and stage III at diagnosis were 32.4%, 38.2%, and 29.3%, respectively.
The median number of doses administered was 16 for denosumab and 15 for zoledronic acid.
Efficacy results from study 4 are presented in figure 2 and table 3.
Figure 2. Kaplan-Meier plot for time to first on-study SRE in patients with newly diagnosed multiple myeloma
Table 3. Efficacy results for denosumab compared to zoledronic acid in patients with newly diagnosed multiple myeloma
| | Denosumab (N = 859) | Zoledronic Acid (N = 859) |
| First SRE |
| Number of patients who had SREs (%) | 376 (43.8) | 383 (44.6) |
| Median time to SRE (months) | 22.8 (14.7, NE) | 23.98 (16.56, 33.31) |
| Hazard ratio (95% CI) | 0.98 (0.85, 1.14) |
| First and subsequent SRE |
| Mean number of events/patient | 0.66 | 0.66 |
| Rate ratio (95% CI) | 1.01 (0.89, 1.15) |
| Skeletal morbidity rate per year | 0.61 | 0.62 |
| First SRE or HCM |
| Median time (months) | 22.14 (14.26, NE) | 21.32 (13.86, 29.7) |
| Hazard ratio (95% CI) | 0.98 (0.85, 1.12) |
| First radiation to bone |
| Hazard ratio (95% CI) | 0.78 (0.53, 1.14) |
| Overall survival |
| Hazard ratio (95% CI) | 0.90 (0.70, 1.16) |
NE = not estimable
HCM = hypercalcaemia of malignancy
Clinical efficacy and safety in adults and skeletally mature adolescents with giant cell tumour of bone
The safety and efficacy of denosumab was studied in two phase II open-label, single-arm trials (studies 5 and 6) that enrolled 554 patients with giant cell tumour of bone that was either unresectable or for which surgery would be associated with severe morbidity and a prospective, multicentre, open label, phase IV study (study 7) that provided long term safety follow up for patients who completed study 6. Patients received 120 mg denosumab subcutaneously every 4 weeks with a loading dose of 120 mg on days 8 and 15. Patients who discontinued denosumab then entered the safety follow-up phase for a minimum of 60 months. Retreatment with denosumab while in safety follow-up was allowed for patients who initially demonstrated a response to denosumab (e.g. in the case of recurrent disease).
Study 5 enrolled 37 adult patients with histologically confirmed unresectable or recurrent giant cell tumour of bone. The main outcome measure of the trial was response rate, defined as either at least 90% elimination of giant cells relative to baseline (or complete elimination of giant cells in cases where giant cells represent < 5% of tumour cells), or a lack of progression of the target lesion by radiographic measurements in cases where histopathology was not available. Of the 35 patients included in the efficacy analysis, 85.7% (95% CI: 69.7, 95.2) had a treatment response to denosumab. All 20 patients (100%) with histology assessments met response criteria. Of the remaining 15 patients, 10 (67%) radiographic measurements showed no progression of the target lesion.
Study 6 enrolled 535 adult or skeletally mature adolescents with giant cell tumour of bone. Of these patients, 28 were aged 12-17 years. Patients were assigned to one of three cohorts: cohort 1 included patients with surgically unsalvageable disease (e.g. sacral, spinal, or multiple lesions, including pulmonary metastases); cohort 2 included patients with surgically salvageable disease whose planned surgery was associated with severe morbidity (e.g. joint resection, limb amputation, or hemipelvectomy); cohort 3 included patients previously participating in study 5 and rolled over into this study. The primary objective was to evaluate the safety profile of denosumab in patients with giant cell tumour of bone. The secondary outcome measures of the study included time to disease progression (based on investigator assessment) for cohort 1 and proportion of patients without any surgery at month 6 for cohort 2.
In cohort 1 at the final analysis, 28 of the 260 treated patients (10.8%) had disease progression. In cohort 2, 219 of the 238 (92.0%; 95% CI: 87.8%, 95.1%) evaluable patients treated with denosumab had not undergone surgery by month 6. Of the 239 patients in cohort 2 with baseline target lesion location or on-study location not in lungs or soft tissue, a total of 82 subjects (34.3%) were able to avoid on-study surgery. Overall, efficacy results in skeletally mature adolescents were similar to those observed in adults.
Study 7 enrolled 85 adult patients who were previously enrolled and completed study 6. Patients were allowed to receive denosumab treatment for GCTB, and all patients were followed for 5 years. The primary objective was to evaluate the long-term safety profile of denosumab in patients with giant cell tumour of the bone.
Effect on pain
In the final analysis cohorts 1 and 2 combined, a clinically meaningful reduction in worst pain (i.e. ≥ 2-point decrease from baseline) was reported for 30.8% of patients at risk (i.e. those who had a worst pain score of ≥ 2 at baseline) within 1 week of treatment, and ≥ 50% at week 5. These pain improvements were maintained at all subsequent evaluations.
Paediatric population
The Medicines and Healthcare products Regulatory Agency has waived the obligation to submit the results of studies with denosumab in all subsets of the paediatric population in the prevention of skeletal related events in patients with bone metastases and subsets of the paediatric population below the age of 12 in the treatment of giant cell tumour of bone (see section 4.2 for information on paediatric use).
In study 6, denosumab has been evaluated in a subset of 28 adolescent patients (aged 13-17 years) with giant cell tumour of bone who had reached skeletal maturity defined by at least 1 mature long bone (e.g. closed epiphyseal growth plate of the humerus) and body weight ≥ 45 kg. One adolescent patient with surgically unsalvageable disease (N=14) had disease recurrence during initial treatment. Thirteen of the 14 patients with surgically salvageable disease whose planned surgery was associated with severe morbidity had not undergone surgery by month 6.