CLINICAL PHARMACOLOGY
Mechanism Of Action
ACTONEL has an affinity for hydroxyapatite crystals in bone and acts as an antiresorptive agent. At the
cellular level, ACTONEL inhibits osteoclasts. The osteoclasts adhere normally to the bone surface,
but show evidence of reduced active resorption (for example, lack of ruffled border).
Histomorphometry in rats, dogs, and minipigs showed that ACTONEL treatment reduces bone turnover
(activation frequency, that is, the rate at which bone remodeling sites are activated) and bone resorption
at remodeling sites.
Pharmacodynamics
ACTONEL treatment decreases the elevated rate of bone turnover that is typically seen in
postmenopausal osteoporosis. In clinical trials, administration of ACTONEL to postmenopausal women
resulted in decreases in biochemical markers of bone turnover, including urinary
deoxypyridinoline/creatinine and urinary collagen cross-linked N-telopeptide (markers of bone
resorption) and serum bone-specific alkaline phosphatase (a marker of bone formation). At the 5 mg
dose, decreases in deoxypyridinoline/creatinine were evident within 14 days of treatment. Changes in
bone formation markers were observed later than changes in resorption markers, as expected, due to the
coupled nature of bone resorption and bone formation; decreases in bone-specific alkaline phosphatase
of about 20% were evident within 3 months of treatment. Bone turnover markers reached a nadir of
about 40% below baseline values by the sixth month of treatment and remained stable with continued
treatment for up to 3 years. Bone turnover is decreased as early as 14 days and maximally within about 6
months of treatment, with achievement of a new steady-state that more nearly approximates the rate of
bone turnover seen in premenopausal women. In a 1-year study comparing daily versus weekly oral
dosing regimens of ACTONEL for the treatment of osteoporosis in postmenopausal women,
ACTONEL 5 mg daily and ACTONEL 35 mg once-a-week decreased urinary collagen cross-linked Ntelopeptide
by 60% and 61%, respectively. In addition, serum bone-specific alkaline phosphatase was
also reduced by 42% and 41% in the ACTONEL 5 mg daily and ACTONEL 35 mg once-a-week
groups, respectively. When postmenopausal women with osteoporosis were treated for 1 year with
ACTONEL 5 mg daily or ACTONEL 75 mg two consecutive days per month, urinary collagen crosslinked
N-telopeptide was decreased by 54% and 52%, respectively, and serum bone-specific alkaline
phosphatase was reduced by 36% and 35%, respectively. In a 1–year study comparing ACTONEL 5 mg
daily versus ACTONEL 150 mg once-a-month in women with postmenopausal osteoporosis, urinary
collagen cross-linked N-telopeptide was decreased by 52% and 49%, respectively, and serum bonespecific
alkaline phosphatase was reduced by 31% and 32%, respectively.
Osteoporosis In Men
In a 2-year study of men with osteoporosis, treatment with ACTONEL 35 mg once-a-week resulted in a
mean decrease from baseline compared to placebo of 16% (placebo 20%; ACTONEL 35 mg 37%) for
the bone resorption marker urinary collagen cross-linked N-telopeptide, 45% (placebo -6%;
ACTONEL 35 mg 39%) for the bone resorption marker serum C-telopeptide, and 27% (placebo -2%;
ACTONEL 35 mg 25%) for the bone formation marker serum bone-specific alkaline phosphatase.
Glucocorticoid-Induced Osteoporosis
Osteoporosis with glucocorticoid use occurs as a result of inhibited bone formation and increased
bone resorption resulting in net bone loss. ACTONEL decreases bone resorption without directly
inhibiting bone formation.
In two 1-year clinical trials in the treatment and prevention of glucocorticoid-induced osteoporosis,
ACTONEL 5 mg decreased urinary collagen cross-linked N-telopeptide (a marker of bone resorption),
and serum bone-specific alkaline phosphatase (a marker of bone formation) by 50% to 55% and 25% to
30%, respectively, within 3 to 6 months after initiation of therapy.
Paget’s Disease
Paget’s disease of bone is a chronic, focal skeletal disorder characterized by greatly increased and
disordered bone remodeling. Excessive osteoclastic bone resorption is followed by osteoblastic new
bone formation, leading to the replacement of the normal bone architecture by disorganized, enlarged,
and weakened bone structure.
In pagetic patients treated with ACTONEL 30 mg daily for 2 months, bone turnover returned to normal
in a majority of patients as evidenced by significant reductions in serum alkaline phosphatase (a marker
of bone formation), and in urinary hydroxyproline/creatinine and deoxypyridinoline/creatinine (markers
of bone resorption).
Pharmacokinetics
Absorption
Based on simultaneous modeling of serum and urine data, peak absorption after an oral dose is achieved
at approximately 1 hour (T ) and occurs throughout the upper gastrointestinal tract. The fraction of
the dose absorbed is independent of dose over the range studied (single dose, from 2.5 mg to 30 mg;
multiple dose, from 2.5 mg to 5 mg). Steady-state conditions in the serum are observed within 57 days of
daily dosing. Mean absolute oral bioavailability of the 30 mg tablet is 0.63% (90% CI: 0.54% to 0.75%)
and is comparable to a solution.
Food Effect
The extent of absorption of a 30 mg dose (three 10 mg tablets) when administered 0.5 hours before
breakfast is reduced by 55% compared to dosing in the fasting state (no food or drink for 10 hours prior
to or 4 hours after dosing). Dosing 1 hour prior to breakfast reduces the extent of absorption by 30%
compared to dosing in the fasting state. Dosing either 0.5 hours prior to breakfast or 2 hours after
dinner (evening meal) results in a similar extent of absorption. ACTONEL is effective when
administered at least 30 minutes before breakfast.
Distribution
The mean steady-state volume of distribution for risedronate is 13.8 L/kg in humans. Human plasma
protein binding of drug is about 24%. Preclinical studies in rats and dogs dosed intravenously with
single doses of [14C] risedronate indicate that approximately 60% of the dose is distributed to bone.
The remainder of the dose is excreted in the urine. After multiple oral dosing in rats, the uptake of
risedronate in soft tissues was in the range of 0.001% to 0.01%.
Metabolism
There is no evidence of systemic metabolism of risedronate.
Excretion
In young healthy subjects, approximately half of the absorbed dose of risedronate was excreted in urine
within 24 hours, and 85% of an intravenous dose was recovered in the urine over 28 days. Based on
simultaneous modeling of serum and urine data, mean renal clearance was 105 mL/min (CV = 34%) and
mean total clearance was 122 mL/min (CV = 19%), with the difference primarily reflecting nonrenal
clearance or clearance due to adsorption to bone. The renal clearance is not concentration dependent,
and there is a linear relationship between renal clearance and creatinine clearance. Unabsorbed drug is
eliminated unchanged in feces. In osteopenic postmenopausal women, the terminal exponential half-life
was 561 hours, mean renal clearance was 52 mL/min (CV = 25%), and mean total clearance was
73 mL/min (CV = 15%).
Specific Populations
Pediatric
ACTONEL is not indicated for use in pediatric patients [see Pediatric Use].
Gender
Bioavailability and pharmacokinetics following oral administration are similar in men and
women.
Geriatric
Bioavailability and disposition are similar in elderly (greater than 60 years of age) and
younger subjects. No dosage adjustment is necessary.
Race
Pharmacokinetic differences due to race have not been studied.
Renal Impairment
Risedronate is excreted unchanged primarily via the kidney. As compared to persons
with normal renal function, the renal clearance of risedronate was decreased by about 70% in patients
with creatinine clearance of approximately 30 mL/min. ACTONEL is not recommended for use in
patients with severe renal impairment (creatinine clearance less than 30 mL/min) because of lack of
clinical experience. No dosage adjustment is necessary in patients with a creatinine clearance greater
than or equal to 30 mL/min.
Hepatic Impairment
No studies have been performed to assess risedronate’s safety or efficacy in
patients with hepatic impairment. Risedronate is not metabolized in rat, dog, and human liver
preparations. Insignificant amounts (less than 0.1% of intravenous dose) of drug are excreted in the bile
in rats. Therefore, dosage adjustment is unlikely to be needed in patients with hepatic impairment.
Drug Interactions
No specific drug-drug interaction studies were performed. Risedronate is not
metabolized and does not induce or inhibit hepatic microsomal drug-metabolizing enzymes (Cytochrome
P450) [see DRUG INTERACTIONS].
Animal Toxicology And/Or Pharmacology
Risedronate demonstrated potent anti-osteoclast, antiresorptive activity in ovariectomized rats and
minipigs. Bone mass and biomechanical strength were increased dose-dependently at daily oral doses
up to 4 and 25 times the human recommended oral dose of 5 mg for rats and minipigs, respectively.
Risedronate treatment maintained the positive correlation between BMD and bone strength and did not
have a negative effect on bone structure or mineralization. In intact dogs, risedronate induced positive
bone balance at the level of the bone remodeling unit at oral doses ranging from 0.5 to 1.5 times the 5
mg/day human daily dose.
In dogs treated with an oral dose approximately 5 times the human daily dose, risedronate caused a delay
in fracture healing of the radius. The observed delay in fracture healing is similar to other
bisphosphonates. This effect did not occur at a dose approximately 0.5 times the human daily dose.
The Schenk rat assay, based on histologic examination of the epiphyses of growing rats after drug
treatment, demonstrated that risedronate did not interfere with bone mineralization even at the highest
dose tested, which was approximately 3500 times the lowest antiresorptive dose in this model (1.5
mcg/kg/day) and approximately 800 times the human daily dose of 5 mg. This indicates that ACTONEL
administered at the therapeutic dose is unlikely to induce osteomalacia.
Dosing multiples provided above are based on the recommended human dose of 5 mg/day and
normalized using body surface area (mg/m2 ).
Clinical Studies
Treatment Of Osteoporosis In Postmenopausal Women
The fracture efficacy of ACTONEL 5 mg daily in the treatment of postmenopausal osteoporosis was
demonstrated in 2 large, randomized, placebo-controlled, double-blind studies that enrolled a total of
almost 4000 postmenopausal women under similar protocols. The Multinational study (VERT MN)
(ACTONEL 5 mg, N = 408) was conducted primarily in Europe and Australia; a second study was
conducted in North America (VERT NA) (ACTONEL 5 mg, N = 821). Patients were selected on the
basis of radiographic evidence of previous vertebral fracture, and therefore, had established disease.
The average number of prevalent vertebral fractures per patient at study entry was 4 in VERT MN, and
2.5 in VERT NA, with a broad range of baseline BMD levels. All patients in these studies received
supplemental calcium 1000 mg/day. Patients with low 25-hydroxyvitamin D3 levels (approximately 40
nmol/L or less) also received supplemental vitamin D 500 international units/day.
Effect On Vertebral Fractures
Fractures of previously undeformed vertebrae (new fractures) and worsening of pre-existing vertebral
fractures were diagnosed radiographically; some of these fractures were also associated with
symptoms (that is, clinical fractures). Spinal radiographs were scheduled annually and prospectively
planned analyses were based on the time to a patient’s first diagnosed fracture. The primary endpoint for
these studies was the incidence of new and worsening vertebral fractures across the period of 0 to 3
years. ACTONEL 5 mg daily significantly reduced the incidence of new and worsening vertebral
fractures and of new vertebral fractures in both VERT NA and VERT MN at all time points (Table 3).
The reduction in risk seen in the subgroup of patients who had 2 or more vertebral fractures at study
entry was similar to that seen in the overall study population.
Table 3: The Effect of ACTONEL on the Risk of Vertebral Fractures
|
Proportion of Patients
with Fracture (%)a |
|
VERT NA |
Placebo
N = 678 |
ACTONEL 5 mg
N = 696 |
Absolute Risk
Reduction (%) |
Relative Risk
Reduction (%) |
New and Worsening |
01 Year |
7.2 |
3.9 |
3.3 |
49 |
02 Years |
12.8 |
8.0 |
4.8 |
42 |
03 Years |
18.5 |
13.9 |
4.6 |
33 |
New |
01 Year |
6.4 |
2.4 |
4.0 |
65 |
02 Years |
11.7 |
5.8 |
5.9 |
55 |
03 Years |
16.3 |
11.3 |
5.0 |
41 |
VERT MN |
Placebo
N = 346 |
ACTONEL 5 mg
N = 344 |
Absolute Risk
Reduction (%) |
Relative Risk
Reduction (%) |
New and Worsening |
01 Year |
15.3 |
8.2 |
7.1 |
50 |
02 Years |
28.3 |
13.9 |
14.4 |
56 |
03 Years |
34.0 |
21.8 |
12.2 |
46 |
New |
01 Year |
13.3 |
5.6 |
7.7 |
61 |
02 Years |
24.7 |
11.6 |
13.1 |
59 |
03 Years |
29.0 |
18.1 |
10.9 |
49 |
aCalculated by Kaplan-Meier methodology. |
Effect On Osteoporosis-Related Nonvertebral Fractures
In VERT MN and VERT NA, a prospectively planned efficacy endpoint was defined consisting of all
radiographically confirmed fractures of skeletal sites accepted as associated with osteoporosis.
Fractures at these sites were collectively referred to as osteoporosis-related nonvertebral fractures.
ACTONEL 5 mg daily significantly reduced the incidence of nonvertebral osteoporosis-related
fractures over 3 years in VERT NA (8% versus 5%; relative risk reduction 39%) and reduced the
fracture incidence in VERT MN from 16% to 11%. There was a significant reduction from 11% to 7%
when the studies were combined, with a corresponding 36% reduction in relative risk. Figure 1 shows
the overall results as well as the results at the individual skeletal sites for the combined studies.
Figure 1: Nonvertebal Osteoporosis -Related Fractures Cumulative Incidence Over 3 Years
Combined VERT
MN and VERT NA
Effect On Bone Mineral Density
The results of 4 randomized, placebo-controlled trials in women with postmenopausal osteoporosis
(VERT MN, VERT NA, BMD MN, BMD NA) demonstrate that ACTONEL 5 mg daily increases BMD
at the spine, hip, and wrist compared to the effects seen with placebo. Table 4 displays the significant
increases in BMD seen at the lumbar spine, femoral neck, femoral trochanter, and midshaft radius in
these trials compared to placebo. In both VERT studies (VERT MN and VERT NA), ACTONEL 5 mg
daily produced increases in lumbar spine BMD that were progressive over the 3 years of treatment, and
were statistically significant relative to baseline and to placebo at 6 months and at all later time points.
Table 4: Mean Percent Increase in BMD from Baseline in Patients Taking ACTONEL
5 mg or Placebo at Endpointa
|
VERT MNb |
VERT NAb |
BMD MNc |
BMD NAc |
Placebo
N = 323 |
5 mg
N = 323 |
Placebo
N = 599 |
5 mg
N = 606 |
Placebo
N = 161 |
5 mg
N = 148 |
Placebo
N = 191 |
5 mg
N = 193 |
Lumbar Spine |
1.0 |
6.6 |
0.8 |
5.0 |
0.0 |
4.0 |
0.2 |
4.8 |
Femoral Neck |
-1.4 |
1.6 |
-1.0 |
1.4 |
-1.1 |
1.3 |
0.1 |
2.4 |
Femoral Trochanter |
-1.9 |
3.9 |
-0.5 |
3.0 |
-0.6 |
2.5 |
1.3 |
4.0 |
Midshaft Radius |
-1.5* |
0.2* |
-1.2* |
0.1* |
ND |
ND |
aThe endpoint value is the value at the study's last time point for all patients who had
BMD measured at that time; otherwise the last post-baseline BMD value prior to the
study's last time point is used.
bThe duration of the studies was 3 years.
cThe duration of the studies was 1.5 to 2 years.
* BMD of the midshaft radius was measured in a subset of centers in VERT MN
(placebo, N = 222; 5 mg, N = 214) and VERT NA (placebo, N = 310; 5 mg, N = 306).
ND = analysis not done |
ACTONEL 35 mg once-a-week (N = 485) was shown to be non-inferior to ACTONEL 5 mg daily (N =
480) in a 1-year, double-blind, multicenter study of postmenopausal women with osteoporosis. In the
primary efficacy analysis of completers, the mean increases from baseline in lumbar spine BMD at 1
year were 4.0% (3.7, 4.3; 95% confidence interval [CI]) in the 5 mg daily group (N = 391) and 3.9%
(3.6, 4.3; 95% CI) in the 35 mg once-a-week group (N = 387) and the mean difference between 5 mg
daily and 35 mg once-a-week was 0.1% (-0.4, 0.6; 95% CI). The results of the intent-to-treat analysis
with the last observation carried forward were consistent with the primary efficacy analysis of
completers. The 2 treatment groups were also similar with regard to BMD increases at other skeletal
sites.
In a double-blind, multicenter study of postmenopausal women with osteoporosis, treatment with
ACTONEL 75 mg two consecutive days per month (N = 616) was shown to be non-inferior
to ACTONEL 5 mg daily (N = 613). In the primary efficacy analysis of completers, the mean increases
from baseline in lumbar spine BMD at 1 year were 3.6% (3.3, 3.9; 95% CI) in the 5 mg daily group (N =
527) and 3.4% (3.1, 3.7; 95% CI) in the 75 mg two days per month group (N = 524) with a mean
difference between groups being 0.2% (-0.2, 0.6; 95% CI). The results of the intent-to-treat analysis
with the last observation carried forward were consistent with the primary efficacy analysis of
completers. The 2 treatment groups were also similar with regard to BMD increases at other skeletal
sites.
ACTONEL 150 mg once-a-month (N = 650) was shown to be non-inferior to ACTONEL 5 mg daily (N
= 642) in a 1-year, double-blind, multicenter study of postmenopausal women with osteoporosis. The
primary efficacy analysis was conducted in all randomized patients with baseline and post-baseline
lumbar spine BMD values (modified intent-to-treat population) using last observation carried forward.
The mean increases from baseline in lumbar spine BMD at 1 year were 3.4% (3.0, 3.8; 95% CI) in the
5 mg daily group (N = 561), and 3.5% (3.1, 3.9; 95% CI) in the 150 mg once-a-month group (N = 578)
with a mean difference between groups being -0.1% (-0.5, 0.3; 95% CI). The results of the completers
analysis were consistent with the primary efficacy analysis. The 2 treatment groups were also similar
with regard to BMD increases at other skeletal sites.
Histology/Histomorphometry
Bone biopsies from 110 postmenopausal women were obtained at endpoint. Patients had received
placebo or daily ACTONEL (2.5 mg or 5 mg) for 2 to 3 years. Histologic evaluation (N = 103) showed
no osteomalacia, impaired bone mineralization, or other adverse effects on bone in ACTONEL-treated
women. These findings demonstrate that bone formed during ACTONEL administration is of normal
quality. The histomorphometric parameter mineralizing surface, an index of bone turnover, was
assessed based upon baseline and post-treatment biopsy samples from 21 treated with placebo and 23
patients treated with ACTONEL 5 mg. Mineralizing surface decreased moderately in ACTONELa
treated patients (median percent change: placebo, -21%; ACTONEL 5 mg, -74%), consistent with the
known effects of treatment on bone turnover.
Effect On Height
In the two 3-year osteoporosis treatment studies, standing height was measured yearly by stadiometer.
Both ACTONEL and placebo-treated groups lost height during the studies. Patients who received
ACTONEL had a statistically significantly smaller loss of height than those who received placebo. In
VERT MN, the median annual height change was -2.4 mm/yr in the placebo group compared to -1.3
mm/yr in the ACTONEL 5 mg daily group. In VERT NA, the median annual height change was -1.1
mm/yr in the placebo group compared to -0.7 mm/yr in the ACTONEL 5 mg daily group.
Prevention Of Osteoporosis In Postmenopausal Women
The safety and effectiveness of ACTONEL 5 mg daily for the prevention of postmenopausal
osteoporosis were demonstrated in a 2-year, double-blind, placebo-controlled study of 383
postmenopausal women (age range 42 to 63 years) within three years of menopause (ACTONEL 5 mg,
N = 129). All patients in this study received supplemental calcium 1000 mg/day. Increases in BMD were
observed as early as 3 months following initiation of ACTONEL treatment. ACTONEL 5 mg daily
produced significant mean increases in BMD at the lumbar spine, femoral neck, and trochanter compared
to placebo at the end of the study (Figure 2). ACTONEL 5 mg daily was also effective in patients with
lower baseline lumbar spine BMD (more than 1 SD below the premenopausal mean) and in those with
normal baseline lumbar spine BMD. Bone mineral density at the distal radius decreased in both
ACTONEL and placebo-treated women following 1 year of treatment.
Figure 2: Change in BMD from Baseline
2-Year Prevention Study
The safety and effectiveness of ACTONEL 35 mg once-a-week for the prevention postmenopausal
osteoporosis were demonstrated in a 1-year, double-blind, placebo-controlled study of 278 patients
(ACTONEL 35 mg, N = 136). All patients were supplemented with 1000 mg elemental calcium and
400 international units vitamin D per day. The primary efficacy measure was the percent change in
lumbar spine BMD from baseline after 1 year of treatment using LOCF (last observation carried
forward). ACTONEL 35 mg once-a-week resulted in a statistically significant mean difference from
placebo in lumbar spine BMD of +2.9% (least square mean for placebo -1.05%; risedronate +1.83%).
ACTONEL 35 mg once-a-week also showed a statistically significant mean difference from placebo in
BMD at the total proximal femur of +1.5% (placebo -0.53%; risedronate +1.01%), femoral neck of
+1.2% (placebo -1.00%; risedronate +0.22%), and trochanter of +1.8% (placebo -0.74%; risedronate
+1.07%).
Combined Administration With Hormone Replacement Therapy
The effects of combining ACTONEL 5 mg daily with conjugated estrogen 0.625 mg daily (N = 263)
were compared to the effects of conjugated estrogen alone (N = 261) in a 1-year, randomized, doubleblind
study of women ages 37 to 82 years, who were on average 14 years postmenopausal. The BMD
results for this study are presented in Table 5.
Table 5 Percent Change from Baseline in BMD After 1
Year of Treatment
|
Estrogen 0.625 mg
N = 261 |
ACTONEL 5 mg +
Estrogen 0.625 mg
N = 263 |
Lumbar Spine |
4.6 ± 0.20 |
5.2 ± 0.23 |
Femoral Neck |
1.8 ± 0.25 |
2.7 ± 0.25 |
Femoral Trochanter |
3.2 ± 0.28 |
3.7 ± 0.25 |
Midshaft Radius |
0.4 ± 0.14 |
0.7 ± 0.17 |
Distal Radius |
1.7 ± 0.24 |
1.6 ± 0.28 |
Values shown are mean (±SEM) percent change from baseline. |
Histology/Histomorphometry
Bone biopsies from 53 postmenopausal women were obtained at endpoint. Patients had received
ACTONEL 5 mg plus estrogen or estrogen-alone once daily for 1 year. Histologic evaluation (N = 47)
demonstrated that the bone of patients treated with ACTONEL plus estrogen was of normal lamellar
structure and normal mineralization. The histomorphometric parameter mineralizing surface, a measure
of bone turnover, was assessed based upon baseline and post-treatment biopsy samples from 12 patients
treated with ACTONEL plus estrogen and 12 treated with estrogen-alone. Mineralizing surface
decreased in both treatment groups (median percent change: ACTONEL plus estrogen, -79%; estrogenalone,
-50%), consistent with the known effects of these agents on bone turnover.
Men With Osteoporosis
The effects of ACTONEL 35 mg once-a-week on BMD were examined in a 2-year, double-blind,
placebo-controlled, multinational study in 285 men with osteoporosis (ACTONEL, N = 192). The
patients had a mean age of 61 years (range 36 to 84 years) and 95% were Caucasian. At baseline, mean
lumbar spine T-score was -3.2 and mean femoral neck T-score was -2.4. All patients in the study had
either, 1) a BMD T-score less than or equal to -2 at the femoral neck and less than or equal to -1 at the
lumbar spine, or 2) a BMD T-score less than or equal to -1 at the femoral neck and less than or equal
to -2.5 at the lumbar spine. All patients were supplemented with calcium 1000 mg/day and vitamin D 400
to 500 international units/day. ACTONEL 35 mg once-a-week produced significant mean increases in
BMD at the lumbar spine, femoral neck, trochanter, and total hip compared to placebo after 2 years of
treatment (treatment difference: lumbar spine, 4.5%; femoral neck, 1.1%; trochanter, 2.2%; total proximal
femur, 1.5%).
Glucocorticoid-Induced Osteoporosis
Bone Mineral Density
Two 1-year, double-blind, placebo-controlled trials in patients who were taking greater than or equal to
7.5 mg/day of prednisone or equivalent demonstrated that ACTONEL 5 mg daily was effective in the
prevention and treatment of glucocorticoid-induced osteoporosis in men and women who were either
initiating or continuing glucocorticoid therapy. The efficacy of ACTONEL therapy for
glucocorticoid-induced osteoporosis beyond one year has not been studied.
The prevention study enrolled 228 patients (ACTONEL 5 mg, N = 76) (18 to 85 years of age), each of
whom had initiated glucocorticoid therapy (mean daily dose of prednisone 21 mg) within the previous 3
months (mean duration of use prior to study 1.8 months) for rheumatic, skin, and pulmonary diseases.
The mean lumbar spine BMD was normal at baseline (average T-score -0.7). All patients in this study
received supplemental calcium 500 mg/day. By the third month of treatment, and continuing through the
year-long treatment, the placebo group experienced losses in BMD at the lumbar spine, femoral neck,
and trochanter, while BMD was maintained or increased in the ACTONEL 5 mg group. At each skeletal
site there were statistically significant differences between the placebo group and the ACTONEL 5 mg
group at all timepoints (Months 3, 6, 9, and 12). The treatment differences increased with continued
treatment. Although BMD increased at the distal radius in the ACTONEL 5 mg group compared to the
placebo group, the difference was not statistically significant. The differences between placebo and
ACTONEL 5 mg after 1 year were 3.8% at the lumbar spine, 4.1% at the femoral neck, and 4.6% at the
trochanter, as shown in Figure 3. The results at these skeletal sites were similar to the overall results
when the subgroups of men and postmenopausal women, but not premenopausal women, were analyzed
separately. ACTONEL was effective at the lumbar spine, femoral neck, and trochanter regardless of
age (less than 65 vs. greater than or equal to 65), gender, prior and concomitant glucocorticoid dose, or
baseline BMD. Positive treatment effects were also observed in patients taking glucocorticoids for a
broad range of rheumatologic disorders, the most common of which were rheumatoid arthritis, temporal
arteritis, and polymyalgia rheumatica.
The treatment study of similar design enrolled 290 patients (ACTONEL 5 mg, N = 100) (19 to 85 years
of age) with continuing, long-term (greater than or equal to 6 months) use of glucocorticoids (mean
duration of use prior to study 60 months; mean daily dose of prednisone 15 mg) for rheumatic, skin, and
pulmonary diseases. The baseline mean lumbar spine BMD was low (1.63 SD below the young healthy
population mean), with 28% of the patients more than 2.5 SD below the mean. All patients in this study
received supplemental calcium 1000 mg/day and vitamin D 400 international units/day.
After 1 year of treatment, the BMD of the placebo group was within 1% of baseline levels at the lumbar
spine, femoral neck, and trochanter. ACTONEL 5 mg increased BMD at the lumbar spine (2.9%),
femoral neck (1.8%), and trochanter (2.4%). The differences between ACTONEL and placebo were
2.7% at the lumbar spine, 1.9% at the femoral neck, and 1.6% at the trochanter as shown in Figure 4. The
differences were statistically significant for the lumbar spine and femoral neck, but not at the femoral
trochanter. ACTONEL was similarly effective on lumbar spine BMD regardless of age (less than 65
vs. greater than or equal to 65), gender, or pre-study glucocorticoid dose. Positive treatment effects
were also observed in patients taking glucocorticoids for a broad range of rheumatologic disorders,
the most common of which were rheumatoid arthritis, temporal arteritis, and polymyalgia rheumatica.
Figure 3: Change in BMD from Baseline Patients Recently Initiating Glucocorticoid Therapy
Figure 4: Change in BMD from Baseline Patients on Long -Term Glucocorticoid Therapy
Vertebral Fractures
In the prevention study of patients initiating glucocorticoids, the incidence of vertebral fractures at 1
year was reduced from 17% in the placebo group to 6% in the ACTONEL group. In the treatment study
of patients continuing glucocorticoids, the incidence of vertebral fractures was reduced from 15% in
the placebo group to 5% in the ACTONEL group (Figure 5). The statistically significant reduction in
vertebral fracture incidence in the analysis of the combined studies corresponded to an absolute risk
reduction of 11% and a relative risk reduction of 70%. All vertebral fractures were diagnosed
radiographically; some of these fractures also were associated with symptoms (that is, clinical
fractures).
Figure 5: Incidence of Vertebral Fractures in Patients Initiating or Continuing Glucocorticoid Therapy
Histology/Histomorphometry
Bone biopsies from 40 patients on glucocorticoid therapy were obtained at endpoint. Patients had
received placebo or daily ACTONEL (2.5 mg or 5 mg) for 1 year. Histologic evaluation (N = 33)
showed that bone formed during treatment with ACTONEL was of normal lamellar structure and normal
mineralization, with no bone or marrow abnormalities observed. The histomorphometric parameter
mineralizing surface, a measure of bone turnover, was assessed based upon baseline and post-treatment
biopsy samples from 10 patients treated with ACTONEL 5 mg. Mineralizing surface decreased 24%
(median percent change) in these patients. Only a small number of placebo-treated patients had both
baseline and post-treatment biopsy samples, precluding a meaningful quantitative assessment.
Treatment Of Paget’s Disease
The efficacy of ACTONEL was demonstrated in 2 clinical studies involving 120 men and 65 women. In
a double-blind, active-controlled study of patients with moderate-to-severe Paget’s disease (serum
alkaline phosphatase levels of at least 2 times the upper limit of normal), patients were treated with
ACTONEL 30 mg daily for 2 months or Didronel (etidronate disodium) 400 mg daily for 6 months. At
Day 180, 77% (43/56) of ACTONEL-treated patients achieved normalization of serum alkaline
phosphatase levels, compared to 10.5% (6/57) of patients treated with Didronel (p less than 0.001). At
Day 540, 16 months after discontinuation of therapy, 53% (17/32) of ACTONEL-treated patients and
14% (4/29) of Didronel-treated patients with available data remained in biochemical remission.
During the first 180 days of the active-controlled study, 85% (51/60) of ACTONEL-treated patients
demonstrated a greater than or equal to 75% reduction from baseline in serum alkaline phosphatase
excess (difference between measured level and midpoint of the normal range) with 2 months of treatment
compared to 20% (12/60) in the Didronel-treated group with 6 months of treatment (p less than 0.001).
Changes in serum alkaline phosphatase excess over time (shown in Figure 6) were significant
following only 30 days of treatment, with a 36% reduction in serum alkaline phosphatase excess at that
time compared to only a 6% reduction seen with Didronel treatment at the same time point (p less than
0.01).
Figure 6: Mean Percent Change from Baseline in Serum Alkaline Phosphatase Excess by Visit
Response to ACTONEL therapy was similar in patients with mild to very severe Paget’s disease. Table
6 shows the mean percent reduction from baseline at Day 180 in excess serum alkaline phosphatase in
patients with mild, moderate, or severe disease.
Table 6 Mean Percent Reduction from Baseline at Day
180 in Total Serum Alkaline Phosphatase Excess by
Disease Severity
|
ACTONEL 30 mg |
Didronel 400 mg |
Subgroup:
Baseline
Disease
Severity
(AP) |
n |
Baseline
Serum
AP
(U/L)* |
Mean
%
Reduction |
n |
Baseline
Serum
AP
(U/L)* |
Mean
%
Reduction |
greater
than 2, less
than 3x
ULN |
32 |
271.6 ±
5.3 |
-88.1 |
22 |
277.9 ±
7.45 |
-44.6 |
greater
than or
equal to 3,
less than
7x ULN |
14 |
475.3 ±
28.8 |
-87.5 |
25 |
480.5 ±
26.44 |
-35.0 |
greater
than or equal to 7x
ULN |
8 |
1336.5 ±
134.19 |
-81.8 |
6 |
1331.5 ±
167.58 |
-47.2 |
*Values shown are mean ± SEM; ULN = upper limit of
normal. |
Response to ACTONEL therapy was similar between patients who had previously received anti-pagetic
therapy and those who had not. In the active-controlled study, 4 patients previously non-responsive to 1
or more courses of anti-pagetic therapy (calcitonin, Didronel) responded to treatment with ACTONEL
30 mg daily (defined by at least a 30% change from baseline). Each of these patients achieved at least
90% reduction from baseline in serum alkaline phosphatase excess, with 3 patients achieving
normalization of serum alkaline phosphatase levels.
Histomorphometry of the bone was studied in 14 patients with bone biopsies: 9 patients had biopsies
from pagetic bone lesions and 5 patients from non-pagetic bone. Bone biopsy results in non-pagetic
bone did not reveal osteomalacia, impairment of bone remodeling, or induction of a significant decline
in bone turnover in patients treated with ACTONEL.