CLINICAL PHARMACOLOGY
Mechanism Of Action
Prolia binds to RANKL, a
transmembrane or soluble protein essential for the formation, function, and
survival of osteoclasts, the cells responsible for bone resorption. Prolia
prevents RANKL from activating its receptor, RANK, on the surface of
osteoclasts and their precursors. Prevention of the RANKL/RANK interaction
inhibits osteoclast formation, function, and survival, thereby decreasing bone
resorption and increasing bone mass and strength in both cortical and
trabecular bone.
Pharmacodynamics
In clinical studies, treatment
with 60 mg of Prolia resulted in reduction in the bone resorption marker serum
type 1 C-telopeptide (CTX) by approximately 85% by 3 days, with maximal
reductions occurring by 1 month. CTX levels were below the limit of assay
quantitation (0.049 ng/mL) in 39% to 68% of patients 1 to 3 months after dosing
of Prolia. At the end of each dosing interval, CTX reductions were partially
attenuated from a maximal reduction of ≥ 87% to ≥ 45% (range: 45%
to 80%), as serum denosumab levels diminished, reflecting the reversibility of
the effects of Prolia on bone remodeling. These effects were sustained with
continued treatment. Upon reinitiation, the degree of inhibition of CTX by
Prolia was similar to that observed in patients initiating Prolia treatment.
Consistent with the
physiological coupling of bone formation and resorption in skeletal remodeling,
subsequent reductions in bone formation markers (i.e. osteocalcin and
procollagen type 1 N-terminal peptide [PlNP]) were observed starting 1 month
after the first dose of Prolia. After discontinuation of Prolia therapy,
markers of bone resorption increased to levels 40% to 60% above pretreatment
values but returned to baseline levels within 12 months.
Pharmacokinetics
In a study conducted in healthy
male and female volunteers (n = 73, age range: 18 to 64 years) following a
single subcutaneously administered Prolia dose of 60 mg after fasting (at least
for 12 hours), the mean maximum denosumab concentration (Cmax) was 6.75 mcg/mL
(standard deviation [SD] = 1.89 mcg/mL). The median time to maximum denosumab
concentration (Tmax) was 10 days (range: 3 to 21 days). After Cmax, serum
denosumab concentrations declined over a period of 4 to 5 months with a mean
half-life of 25.4 days (SD = 8.5 days; n = 46). The mean
area-under-the-concentration-time curve up to 16 weeks (AUC0-16 weeks) of
denosumab was 316 mcg•day/mL (SD = 101 mcg•day/mL).
No accumulation or change in
denosumab pharmacokinetics with time was observed upon multiple dosing of 60 mg
subcutaneously administered once every 6 months.
Prolia pharmacokinetics were not affected by the
formation of binding antibodies.
A population pharmacokinetic analysis was performed to
evaluate the effects of demographic characteristics. This analysis showed no
notable differences in pharmacokinetics with age (in postmenopausal women),
race, or body weight (36 to 140 kg).
Seminal Fluid Pharmacokinetic Study
Serum and seminal fluid concentrations of denosumab were
measured in 12 healthy male volunteers (age range: 43-65 years). After a single
60 mg subcutaneous administration of denosumab, the mean (± SD) Cmax values in
the serum and seminal fluid samples were 6170 (± 2070) and 100 (± 81.9) ng/mL,
respectively, resulting in a maximum seminal fluid concentration of
approximately 2% of serum levels. The median (range) Tmax values in the serum
and seminal fluid samples were 8.0 (7.9 to 21) and 21 (8.0 to 49) days,
respectively. Among the subjects, the highest denosumab concentration in
seminal fluid was 301 ng/mL at 22 days post-dose. On the first day of
measurement (10 days post-dose), nine of eleven subjects had quantifiable
concentrations in semen. On the last day of measurement (106 days post-dose),
five subjects still had quantifiable concentrations of denosumab in seminal
fluid, with a mean (± SD) seminal fluid concentration of 21.1 (± 36.5) ng/mL
across all subjects (n = 12).
Drug Interactions
In a study of 19 postmenopausal women with low BMD and
rheumatoid arthritis treated with etanercept (50 mg subcutaneous injection once
weekly), a single-dose of denosumab (60 mg subcutaneous injection) was
administered 7 days after the previous dose of etanercept. No clinically
significant changes in the pharmacokinetics of etanercept were observed.
Cytochrome P450 Substrates
In a study of 17 postmenopausal women with osteoporosis,
midazolam (2 mg oral) was administered 2 weeks after a single-dose of denosumab
(60 mg subcutaneous injection), which approximates the Tmax of denosumab.
Denosumab did not affect the pharmacokinetics of midazolam, which is
metabolized by cytochrome P450 3A4 (CYP3A4). This indicates that denosumab
should not alter the pharmacokinetics of drugs metabolized by CYP3A4 in
postmenopausal women with osteoporosis.
Specific Populations
Gender
Mean serum denosumab concentration-time profiles observed
in a study conducted in healthy men ≥ 50 years were similar to those
observed in a study conducted in postmenopausal women using the same dose
regimen.
Age
The pharmacokinetics of denosumab were not affected by
age across all populations studied whose ages ranged from 28 to 87 years.
Race
The pharmacokinetics of denosumab were not affected by
race.
Renal Impairment
In a study of 55 patients with varying degrees of renal
function, including patients on dialysis, the degree of renal impairment had no
effect on the pharmacokinetics of denosumab; thus, dose adjustment for renal impairment
is not necessary.
Hepatic Impairment
No clinical studies have been conducted to evaluate the
effect of hepatic impairment on the pharmacokinetics of denosumab.
Animal Toxicology And/Or Pharmacology
Denosumab is an inhibitor of osteoclastic bone resorption
via inhibition of RANKL.
In ovariectomized monkeys, once-monthly treatment with
denosumab suppressed bone turnover and increased bone mineral density (BMD) and
strength of cancellous and cortical bone at doses 50-fold higher than the
recommended human dose of 60 mg administered once every 6 months, based on body
weight (mg/kg). Bone tissue was normal with no evidence of mineralization
defects, accumulation of osteoid, or woven bone.
Because the biological activity of denosumab in animals
is specific to nonhuman primates, evaluation of genetically engineered
(“knockout”) mice or use of other biological inhibitors of the RANK/RANKL
pathway, namely OPG-Fc, provided additional information on the pharmacodynamic
properties of denosumab. RANK/RANKL knockout mice exhibited absence of lymph
node formation, as well as an absence of lactation due to inhibition of mammary
gland maturation (lobulo-alveolar gland development during pregnancy). Neonatal
RANK/RANKL knockout mice exhibited reduced bone growth and lack of tooth
eruption. A corroborative study in 2-week-old rats given the RANKL inhibitor
OPG-Fc also showed reduced bone growth, altered growth plates, and impaired
tooth eruption. These changes were partially reversible in this model when
dosing with the RANKL inhibitors was discontinued.
Clinical Studies
Treatment Of Postmenopausal Women With Osteoporosis
The efficacy and safety of Prolia in the treatment of
postmenopausal osteoporosis was demonstrated in a 3-year, randomized,
double-blind, placebo-controlled trial. Enrolled women had a baseline BMD
T-score between -2.5 and -4.0 at either the lumbar spine or total hip. Women
with other diseases (such as rheumatoid arthritis, osteogenesis imperfecta, and
Paget's disease) or on therapies that affect bone were excluded from this
study. The 7808 enrolled women were aged 60 to 91 years with a mean age of 72
years. Overall, the mean baseline lumbar spine BMD T-score was -2.8, and 23% of
women had a vertebral fracture at baseline. Women were randomized to receive
subcutaneous injections of either placebo (N = 3906) or Prolia 60 mg (N = 3902)
once every 6 months. All women received at least 1000 mg calcium and 400 IU
vitamin D supplementation daily.
The primary efficacy variable was the incidence of new
morphometric (radiologically-diagnosed) vertebral fractures at 3 years.
Vertebral fractures were diagnosed based on lateral spine radiographs  (T4-L4)
using a semiquantitative scoring method. Secondary efficacy variables included
the incidence of hip fracture and nonvertebral fracture, assessed at 3 years.
Effect On Vertebral Fractures
Prolia significantly reduced the incidence of new
morphometric vertebral fractures at 1, 2, and 3 years (p < 0.0001), as shown
in Table 3. The incidence of new vertebral fractures at year 3 was 7.2% in the
placebo-treated women compared to 2.3% for the Prolia-treated women. The
absolute risk reduction was 4.8% and relative risk reduction was 68% for new
morphometric vertebral fractures at year 3.
Table 3: The Effect of Prolia on the Incidence of New
Vertebral Fractures in Postmenopausal Women
|
Proportion of Women with F racture (%)+ |
Absolute Risk Reduction (%)* (95% CI) |
Relative Risk Reduction (%)* (95% CI) |
Placebo
N = 3691 (%) |
Prolia
N = 3702 (%) |
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) |
+ Event rates based on crude rates in each interval.
* Absolute risk reduction and relative risk reduction
based on Mantel-Haenszel method adjusting for age group variable. |
Prolia was effective in
reducing the risk for new morphometric vertebral fractures regardless of age,
baseline rate of bone turnover, baseline BMD, baseline history of fracture, or
prior use of a drug for osteoporosis.
Effect On Hip Fractures
The incidence of hip fracture
was 1.2% for placebo-treated women compared to 0.7% for Prolia-treated women at
year 3. The age-adjusted absolute risk reduction of hip fractures was 0.3% with
a relative risk reduction of 40% at 3 years (p = 0.04) (Figure 1).
Figure 1: Cumulative Incidence of Hip Fractures Over 3
Years
Effect On Nonvertebral
Fractures
Treatment with Prolia resulted
in a significant reduction in the incidence of nonvertebral fractures (Table
4).
Table 4: The Effect of
Prolia on the Incidence of Nonvertebral Fractures at Year 3
|
Proportion of Women with Fracture (%)+ |
Absolute Risk Reduction (%) (95% CI) |
Relative Risk Reduction (%) (95% CI) |
Placebo
N = 3906 (%) |
Prolia
N = 3902 (%) |
Nonvertebral fracture1 |
8.0 |
6.5 |
1.5 (0.3, 2.7) |
20 (5, 33)* |
+ Event rates based on Kaplan-Meier estimates at 3 years.
1 Excluding those of the vertebrae (cervical, thoracic, and lumbar),
skull, facial, mandible, metacarpus, and finger and toe phalanges.
* p-value = 0.01. |
Effect On Bone Mineral Density
(BMD)
Treatment with Prolia
significantly increased BMD at all anatomic sites measured at 3 years. The
treatment differences in BMD at 3 years were 8.8% at the lumbar spine, 6.4% at
the total hip, and 5.2% at the femoral neck. Consistent effects on BMD were observed
at the lumbar spine, regardless of baseline age, race, weight/body mass index
(BMI), baseline BMD, and level of bone turnover.
After Prolia discontinuation,
BMD returned to approximately baseline levels within 12 months.
Bone Histology And Histomorphometry
A total of 115 transiliac crest bone biopsy specimens
were obtained from 92 postmenopausal women with osteoporosis at either month 24
and/or month 36 (53 specimens in Prolia group, 62 specimens in placebo group).
Of the biopsies obtained, 115 (100%) were adequate for qualitative histology
and 7 (6%) were adequate for full quantitative histomorphometry assessment.
Qualitative histology assessments showed normal
architecture and quality with no evidence of mineralization defects, woven
bone, or marrow fibrosis in patients treated with Prolia.
The presence of double tetracycline labeling in a biopsy
specimen provides an indication of active bone remodeling, while the absence of
tetracycline label suggests suppressed bone formation. In patients treated with
Prolia, 35% had no tetracycline label present at the month 24 biopsy and 38%
had no tetracycline label present at the month 36 biopsy, while 100% of
placebo-treated patients had double label present at both time points. When
compared to placebo, treatment with Prolia resulted in virtually absent
activation frequency and markedly reduced bone formation rates. However, the
long-term consequences of this degree of suppression of bone remodeling are
unknown.
Treatment To Increase Bone Mass In Men With Osteoporosis
The efficacy and safety of Prolia in the treatment to
increase bone mass in men with osteoporosis was demonstrated in a 1-year,
randomized, double-blind, placebo-controlled trial. Enrolled men had a baseline
BMD T-score between -2.0 and -3.5 at the lumbar spine or femoral neck. Men with
a BMD T-score between -1.0 and -3.5 at the lumbar spine or femoral neck were
also enrolled if there was a history of prior fragility fracture. Men with
other diseases (such as rheumatoid arthritis, osteogenesis imperfecta, and
Paget’s disease) or on therapies that may affect bone were excluded from this
study. The 242 men enrolled in the study ranged in age from 31 to 84 years with
a mean age of 65 years. Men were randomized to receive SC injections of either
placebo (n = 121) or Prolia 60 mg (n = 121) once every 6 months. All men
received at least 1000 mg calcium and at least 800 IU vitamin D supplementation
daily.
Effect On Bone Mineral Density (BMD)
The primary efficacy variable was percent change in
lumbar spine BMD from baseline to 1-year. Secondary efficacy variables included
percent change in total hip, and femoral neck BMD from baseline to 1-year.
Treatment with Prolia significantly increased BMD at
1-year. The treatment differences in BMD at 1-year were 4.8% (+0.9% placebo,
+5.7% Prolia; (95% CI: 4.0, 5.6); p < 0.0001) at the lumbar spine, 2.0%
(+0.3% placebo, +2.4% Prolia) at the total hip, and 2.2% (0.0% placebo, +2.1%
Prolia) at femoral neck. Consistent effects on BMD were observed at the lumbar
spine regardless of baseline age, race, BMD, testosterone concentrations, and
level of bone turnover.
Bone Histology And Histomorphometry
A total of 29 transiliac crest bone biopsy specimens were
obtained from men with osteoporosis at 12 months (17 specimens in Prolia group,
12 specimens in placebo group). Of the biopsies obtained, 29 (100%) were
adequate for qualitative histology and, in Prolia patients, 6 (35%) were
adequate for full quantitative histomorphometry assessment. Qualitative
histology assessments showed normal architecture and quality with no evidence
of mineralization defects, woven bone, or marrow fibrosis in patients treated
with Prolia. The presence of double tetracycline labeling in a biopsy specimen
provides an indication of active bone remodeling, while the absence of
tetracycline label suggests suppressed bone formation. In patients treated with
Prolia, 6% had no tetracycline label present at the month 12 biopsy, while 100%
of placebo-treated patients had double label present. When compared to placebo,
treatment with Prolia resulted in markedly reduced bone formation rates.
However, the long-term consequences of this degree of suppression of bone
remodeling are unknown.
Treatment Of Glucocorticoid-Induced Osteoporosis
The efficacy and safety of Prolia in the treatment of
patients with glucocorticoid-induced osteoporosis was assessed in the 12-month
primary analysis of a 2-year, randomized, multicenter, double-blind, parallel-group,
active-controlled study (NCT 01575873) of 795 patients (70% women and 30% men)
aged 20 to 94 years (mean age of 63 years) treated with greater than or equal
to 7.5 mg/day oral prednisone (or equivalent) for < 3 months prior to study
enrollment and planning to continue treatment for a total of at least 6 months
(glucocorticoid-initiating subpopulation; n = 290) or ≥ 3 months prior to
study enrollment and planning to continue treatment for a total of at least 6
months (glucocorticoid-continuing subpopulation, n = 505). Enrolled patients
< 50 years of age were required to have a history of osteoporotic fracture.
Enrolled patients ≥ 50 years of age who were in the
glucocorticoid-continuing subpopulation were required to have a baseline BMD T-score
of ≤ -2.0 at the lumbar spine, total hip, or femoral neck; or a BMD
T-score ≤ -1.0 at the lumbar spine, total hip, or femoral neck and a
history of osteoporotic fracture.
Patients were randomized (1:1) to receive either an oral
daily bisphosphonate (active-control, risedronate 5 mg once daily) (n = 397) or
Prolia 60 mg subcutaneously once every 6 months (n = 398) for one year.
Randomization was stratified by gender within each subpopulation. Patients
received at least 1000 mg calcium and 800 IU vitamin D supplementation daily.
Effect On Bone Mineral Density (BMD)
In the glucocorticoid-initiating subpopulation, Prolia
significantly increased lumbar spine BMD compared to the active-control at one
year (Active-control 0.8%, Prolia 3.8%) with a treatment difference of 2.9% (p
< 0.001). In the glucocorticoid-continuing subpopulation, Prolia
significantly increased lumbar spine BMD compared to active-control at one year
(Active-control 2.3%, Prolia 4.4%) with a treatment difference of 2.2% (p <
0.001). Consistent effects on lumbar spine BMD were observed regardless of
gender; race; geographic region; menopausal status; and baseline age, lumbar
spine BMD T-score, and glucocorticoid dose within each subpopulation.
Bone Histology
Bone biopsy specimens were obtained from 17 patients (11
in the active-control treatment group and 6 in the Prolia treatment group) at
Month 12. Of the biopsies obtained, 17 (100%) were adequate for qualitative
histology. Qualitative assessments showed bone of normal architecture and
quality without mineralization defects or bone marrow abnormality. The presence
of double tetracycline labeling in a biopsy specimen provides an indication of
active bone remodeling, while the absence of tetracycline label suggests
suppressed bone formation. In patients treated with active-control, 100% of
biopsies had tetracycline label. In patients treated with Prolia, 1 (33%) had
tetracycline label and 2 (67%) had no tetracycline label present at the 12-month
biopsy. Evaluation of full quantitative histomorphometry including bone
remodeling rates was not possible in the glucocorticoid-induced osteoporosis
population treated with Prolia. The long-term consequences of this degree of
suppression of bone remodeling in glucocorticoid-treated patients is unknown.
Treatment Of Bone Loss In Men With Prostate Cancer
The efficacy and safety of Prolia in the treatment of
bone loss in men with nonmetastatic prostate cancer receiving androgen
deprivation therapy (ADT) were demonstrated in a 3-year, randomized (1:1),
double-blind, placebo-controlled, multinational study. Men less than 70 years
of age had either a BMD T-score at the lumbar spine, total hip, or femoral neck
between -1.0 and -4.0, or a history of an osteoporotic fracture. The mean
baseline lumbar spine BMD T-score was -0.4, and 22% of men had a vertebral
fracture at baseline. The 1468 men enrolled ranged in age from 48 to 97 years
(median 76 years). Men were randomized to receive subcutaneous injections of
either placebo (n = 734) or Prolia 60 mg (n = 734) once every 6 months for a
total of 6 doses. Randomization was stratified by age (< 70 years vs.
≥ 70 years) and duration of ADT at trial entry (≤ 6 months vs. >
6 months). Seventy-nine percent of patients received ADT for more than 6 months
at study entry. All men received at least 1000 mg calcium and 400 IU vitamin D
supplementation daily.
Effect On Bone Mineral Density (BMD)
The primary efficacy variable was percent change in
lumbar spine BMD from baseline to month 24. An additional key secondary
efficacy variable was the incidence of new vertebral fracture through month 36
diagnosed based on x-ray evaluation by two independent radiologists. Lumbar
spine BMD was higher at 2 years in Prolia-treated patients as compared to
placebo-treated patients [-1.0% placebo, +5.6% Prolia; treatment difference
6.7% (95% CI: 6.2, 7.1); p < 0.0001].
With approximately 62% of patients followed for 3 years,
treatment differences in BMD at 3 years were 7.9% (-1.2% placebo, +6.8% Prolia)
at the lumbar spine, 5.7% (-2.6% placebo, +3.2% Prolia) at the total hip, and
4.9% (-1.8% placebo, +3.0% Prolia) at the femoral neck. Consistent effects on
BMD were observed at the lumbar spine in relevant subgroups defined by baseline
age, BMD, and baseline history of vertebral fracture.
Effect On Vertebral Fractures
Prolia significantly reduced the incidence of new
vertebral fractures at 3 years (p = 0.0125), as shown in Table 5.
Table 5: The Effect of Prolia on the Incidence of New
Vertebral Fractures in Men with Nonmetastatic Prostate Cancer
N |
ew Vertebral Fractures in Men with N |
onmetastatic Prostate Cancer |
Proportion of Men with Fracture (%)+ |
Absolute Risk Reduction (%)* (95% CI) |
Relative Risk Reduction (%)* (95% CI) |
Placebo
N = 673 (%) |
Prolia
N = 679 (%) |
0-1 Year |
1.9 |
0.3 |
1.6 (0.5, 2.8) |
85 (33, 97) |
0-2 Years |
3.3 |
1.0 |
2.2 (0.7, 3.8) |
69 (27, 86) |
0-3 Years |
3.9 |
1.5 |
2.4 (0.7, 4.1) |
62 (22, 81) |
+ Event rates based on crude rates in each interval.
* Absolute risk reduction and relative risk reduction
based on Mantel-Haenszel method adjusting for age group and ADT duration
variables. |
Treatment Of Bone Loss In Women
With Breast Cancer
The efficacy and safety of
Prolia in the treatment of bone loss in women receiving adjuvant aromatase
inhibitor (AI) therapy for breast cancer was assessed in a 2-year, randomized
(1:1), double-blind, placebo-controlled, multinational study. Women had
baseline BMD T-scores between -1.0 to -2.5 at the lumbar spine, total hip, or
femoral neck, and had not experienced fracture after age 25. The mean baseline
lumbar spine BMD T-score was -1.1, and 2.0% of women had a vertebral fracture
at baseline. The 252 women enrolled ranged in age from 35 to 84 years (median
59 years). Women were randomized to receive subcutaneous injections of either
placebo (n = 125) or Prolia 60 mg (n = 127) once every 6 months for a total of
4 doses. Randomization was stratified by duration of adjuvant AI therapy at
trial entry (≤ 6 months vs. > 6 months). Sixty-two percent of patients
received adjuvant AI therapy for more than 6 months at study entry. All
women received at least 1000 mg calcium and 400 IU vitamin D supplementation
daily.
Effect On Bone Mineral Density (BMD)
The primary efficacy variable was percent change in
lumbar spine BMD from baseline to month 12. Lumbar spine BMD was higher at 12
months in Prolia-treated patients as compared to placebo-treated patients
[-0.7% placebo, +4.8% Prolia; treatment difference 5.5% (95% CI: 4.8, 6.3); p
< 0.0001].
With approximately 81% of patients followed for 2 years,
treatment differences in BMD at 2 years were 7.6% (-1.4% placebo, +6.2% Prolia)
at the lumbar spine, 4.7% (-1.0% placebo, +3.8% Prolia) at the total hip, and 3.6%
(-0.8% placebo, +2.8% Prolia) at the femoral neck.