In a 104-week carcinogenicity study, rats were administered daily oral doses up to approximately 8 times the maximum recommended human daily dose. There were no significant drug-induced tumor findings in male or female rats. The high dose male group was terminated early in the study (Week 93) due to excessive toxicity, and data from this group were not included in the statistical evaluation of the study results. In an 80-week carcinogenicity study, mice were administered daily oral doses approximately 6.5 times the human dose. There were no significant drug-induced tumor findings in male or female mice.
Risedronate did not exhibit genetic toxicity in the following assays: In vitro bacterial mutagenesis in Salmonella and E. coli (Ames assay), mammalian cell mutagenesis in CHO/HGPRT assay, unscheduled DNA synthesis in rat hepatocytes and an assessment of chromosomal aberrations in vivo in rat bone marrow. Risedronate was positive in a chromosomal aberration assay in CHO cells at highly cytotoxic concentrations (greater than 675 mcg/mL, survival of 6% to 7%). When the assay was repeated at doses exhibiting appropriate cell survival (29%), there was no evidence of chromosomal damage.
Impairment of Fertility
In female rats, ovulation was inhibited at an oral dose approximately 5 times the human dose. Decreased implantation was noted in female rats treated with doses approximately 2.5 times the human dose. In male rats, testicular and epididymal atrophy and inflammation were noted at approximately 13 times the human dose. Testicular atrophy was also noted in male rats after 13 weeks of treatment at oral doses approximately 5 times the human dose. There was moderate-to-severe spermatid maturation block after 13 weeks in male dogs at an oral dose approximately 8 times the human dose. These findings tended to increase in severity with increased dose and exposure time.
Dosing multiples provided above are based on the recommended human dose of 30 mg/day and normalized using body surface area (mg/m2). Actual doses were 24 mg/kg/day in rats, 32 mg/kg/day in mice, and 8, 16 and 40 mg/kg/day in dogs.
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 3,500 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 risedronate sodium 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).
The fracture efficacy of risedronate sodium 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 4,000 postmenopausal women under similar protocols. The Multinational study (VERT MN) (risedronate sodium 5 mg, N = 408) was conducted primarily in Europe and Australia; a second study was conducted in North America (VERT NA) (risedronate sodium 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 1,000 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 FracturesFractures of previously undeformed vertebrae (new fractures) and worsening of preexisting 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. Risedronate sodium 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.
|Proportion of Patients with Fracture (%)*|
|VERT NA||PlaceboN = 678||Risedronate Sodium5 mg N = 696||Absolute Risk Reduction (%)||Relative Risk Reduction (%)|
|New and Worsening|
|0 to 1 Year||7.2||3.9||3.3||49|
|0 to 2 Years||12.8||8.0||4.8||42|
|0 to 3 Years||18.5||13.9||4.6||33|
|0 to 1 Year||6.4||2.4||4.0||65|
|0 to 2 Years||11.7||5.8||5.9||55|
|0 to 3 Years||16.3||11.3||5.0||41|
|VERT MN||Placebo N = 346||Risedronate Sodium5 mgN = 344||Absolute RiskReduction(%)||Relative RiskReduction(%)|
|New and Worsening|
|0 to 1 Year||15.3||8.2||7.1||50|
|0 to 2 Years||28.3||13.9||14.4||56|
|0 to 3 Years||34.0||21.8||12.2||46|
|0 to 1 Year||13.3||5.6||7.7||61|
|0 to 2 Years||24.7||11.6||13.1||59|
|0 to 3 Years||29.0||18.1||10.9||49|
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. Risedronate sodium 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 Nonvertebral Osteoporosis-Related Fractures Cumulative Incidence Over 3 Years Combined VERT MN and VERT NA
Effect on Bone Mineral DensityThe results of 4 randomized, placebo-controlled trials in women with postmenopausal osteoporosis (VERT MN, VERT NA, BMD MN, BMD NA) demonstrate that risedronate sodium 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), risedronate sodium 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.
|VERT MN *||VERT NA *||BMD MN †||BMD NA †|
|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|
|a The 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.|
ND = analysis not done
Risedronate sodium 35 mg once-a-week (N = 485) was shown to be non-inferior to risedronate sodium 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 risedronate sodium 75 mg two consecutive days per month (N = 616) was shown to be non-inferior to risedronate sodium 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.
Risedronate sodium 150 mg once-a-month (N = 650) was shown to be non-inferior to risedronate sodium 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.
Bone biopsies from 110 postmenopausal women were obtained at endpoint. Patients had received placebo or daily risedronate sodium (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 risedronate sodium-treated women. These findings demonstrate that bone formed during risedronate sodium 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 risedronate sodium 5 mg. Mineralizing surface decreased moderately in risedronate sodium-treated patients (median percent change: placebo, -21%; risedronate sodium 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 risedronate sodium and placebo-treated groups lost height during the studies. Patients who received risedronate sodium 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 risedronate sodium 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 risedronate sodium 5 mg daily group.
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