Clinical Pharmacology for Tymlos
Mechanism Of Action
Abaloparatide is a PTHrP(1-34) analog which acts as an agonist at the PTH1 receptor (PTH1R). This results in activation of the cAMP signaling pathway in target cells. Once-daily administration of abaloparatide stimulates new bone formation on trabecular and cortical bone surfaces by stimulation of osteoblastic activity. In rats and monkeys, abaloparatide had an anabolic effect on bone, demonstrated by increases in BMD and bone mineral content (BMC) that correlated with increases in bone strength at vertebral and/or nonvertebral sites [see Nonclinical Toxicology].
Pharmacodynamics
Effects On Markers Of Bone Turnover
A dose-finding study of abaloparatide administered once daily for 24 weeks in postmenopausal women with osteoporosis demonstrated a dose-response relationship for BMD and bone formation markers.
Daily administration of TYMLOS to postmenopausal women with osteoporosis for 18 months increased the bone formation marker serum procollagen type I N-propeptide (sPINP) and the bone resorption marker serum collagen type I cross-linked C-telopeptide (sCTX). The increase in geometric mean sPINP levels peaked at Month 1 at 93% above baseline in postmenopausal women then decreased slowly over time to 45% above baseline at Month 18. The increase in geometric mean sCTX levels in postmenopausal women peaked at Month 3 at 26% above baseline then decreased to baseline levels by Month 18.
Daily administration of TYMLOS to men with osteoporosis for 12 months increased the bone formation marker sPINP and the bone resorption marker sCTX. The increase in geometric mean sPINP levels peaked at Month 1 at 133% above baseline in men then decreased slowly over time to 84% above baseline at Month 12. The increase in geometric mean sCTX levels in men peaked at Month 6 at 46% above baseline and was 35% above baseline by Month 12.
Cardiac Electrophysiology
A 4-way cross-over thorough QT/QTc study was conducted in 55 healthy subjects who received single doses of placebo, subcutaneous doses of abaloparatide at 80 mcg and 240 mcg (three times the recommended dose), and moxifloxacin 400 mg orally. Abaloparatide increased heart rate, with a mean peak increase of 15 beats per minute (bpm) and 20 bpm at the first time point (15 minutes) after dosing with 80 mcg and 240 mcg, respectively. There were no clinically meaningful effects of abaloparatide on QTcI (individually corrected QT intervals) or cardiac electrophysiology.
Pharmacokinetics
Following seven days of subcutaneous administration of abaloparatide 80 mcg, the mean (SD) abaloparatide exposure was 812 (118) pg/mL for Cmax and 1622 (641) pg·hr/mL for AUC0-24 in postmenopausal women with osteoporosis.
Absorption
The median (range) time to peak concentration of abaloparatide 80 mcg was 0.51 hr (0.25 to 0.52 hr) following subcutaneous administration. The absolute bioavailability of abaloparatide in healthy women after subcutaneous administration of an 80 mcg dose was 36%.
Distribution
The in vitro plasma protein binding of abaloparatide was approximately 70%. The volume of distribution was approximately 50 L.
Elimination
Excretion
The mean (SD) half-life of abaloparatide is approximately 1 h. The peptide fragments are primarily eliminated through renal excretion.
Metabolism
No specific metabolism or excretion studies have been performed with TYMLOS. The metabolism of abaloparatide is consistent with non-specific proteolytic degradation into smaller peptide fragments, followed by elimination by renal clearance.
Specific Populations
Male And Female Subjects
Mean serum abaloparatide concentration-time profiles observed in a study conducted in healthy men with a mean (±SD) age of 53.1 (±6.9) years were comparable to those observed in the healthy women with a mean (±SD) age of 53.7 (±7.1) years using the same dosing regimen.
Geriatric Patients
No age-related differences in abaloparatide pharmacokinetics were observed in men and postmenopausal women ranging from 18 to 85 years of age.
Race
No differences in abaloparatide pharmacokinetics based on race were observed in clinical trials.
Patients With Renal Impairment
A single 80 mcg subcutaneous dose of abaloparatide was administered to male and female patients with renal impairment: 8 patients with mild renal impairment (CLCr 60 to 89 mL/min), 7 patients with moderate renal impairment (CLCr 30 to 59 mL/min), 8 patients with severe renal impairment (CLCr 15 to 29 mL/min), and 8 healthy subjects with normal renal function (CLCr 90 or greater mL/min) matched by sex, age, and body mass index (BMI). Abaloparatide Cmax increased 1.0-, 1.3-, and 1.4-fold in patients with mild, moderate, and severe renal impairment, compared to the healthy subjects with normal renal function. Abaloparatide AUC increased 1.2-, 1.7-, and 2.1-fold in patients with mild, moderate, and severe renal impairment, compared to the healthy subjects with normal renal function. Patients undergoing dialysis were not included in the study.
Drug Interactions
In vitro studies showed that abaloparatide, at therapeutic concentrations, does not inhibit or induce Cytochrome P450 enzymes. Abaloparatide is not a substrate of the renal transporters OAT1, OAT3, OCT2, MATE1, or MATE2K.
Immunogenicity
The observed incidence of anti-drug antibodies is highly dependent on the sensitivity and specificity of the assay. Differences in assay methods preclude meaningful comparisons of the incidence of anti-drug antibodies in the studies described below with the incidence of anti-drug antibodies in other studies, including those of abaloparatide or of other abaloparatide products.
Postmenopausal Women With Osteoporosis
Of the patients receiving TYMLOS for 18 months, 41% (318/773) developed anti-abaloparatide antibodies, and 26% (204/773) developed neutralizing antibodies to abaloparatide. Of the patients with anti-abaloparatide antibodies tested for cross-reactivity, 2.4% (7/297) developed cross-reactivity to PTHrP, of which 3 of the 7 patients developed neutralizing antibodies to PTHrP. Only 0.3% (1/297) developed cross-reactive antibodies to PTH, which were not neutralizing to PTH. Antibody formation did not appear to have any clinically significant impact on safety or efficacy endpoints, including bone mineral density (BMD) response, fracture reduction, or adverse events.
Most of the patients with anti-abaloparatide antibodies during treatment with TYMLOS, 86% (275/318), had follow-up antibody measurements every six months after completion of TYMLOS therapy until seroconverting to antibody negative or lost to follow-up. Among these patients, 127 remained antibody positive at 1 year after discontinuing treatment, 55 remained antibody positive at 2 years, and 6 remained antibody positive at 3 years.
Men with Osteoporosis
Of the male patients receiving TYMLOS for 12 months, 25% (36/142) developed anti-abaloparatide antibodies and 1.4% (2/142) developed neutralizing antibodies to abaloparatide. Of the patients with anti-abaloparatide antibodies tested for cross-reactivity, none developed cross-reactivity to PTHrP or PTH. Antibody formation did not appear to have any clinically significant impact on safety or efficacy endpoints, including bone mineral density (BMD) response or adverse events.
Animal Toxicology And Pharmacology
In toxicity studies in rats and monkeys of up to 26-week and 39-week duration, respectively, findings included vasodilation, increases in serum calcium, decreases in serum phosphorus, and soft tissue mineralization at doses ≥10 mcg/kg/day. The 10 mcg/kg/day dose resulted in systemic exposures to abaloparatide in rats and monkeys that were 2 and 3 times, respectively, the exposure in humans at daily subcutaneous doses of 80 mcg.
Pharmacologic effects of abaloparatide on the skeleton were assessed in 12- and 16-month studies in ovariectomized (OVX) rats and monkeys, at doses up to 11- and 1-times human exposure at the recommended subcutaneous dose of 80 mcg, respectively (based on AUC comparisons). In these animal models of postmenopausal osteoporosis, treatment with abaloparatide resulted in dosedependent increases in bone mass at vertebral and/or nonvertebral sites, correlating with increases in bone strength. The anabolic effect of abaloparatide was due to the predominant increase in osteoblastic bone formation and was evidenced by increases in trabecular thickness and/or cortical thickness due to endosteal bone apposition. Abaloparatide maintained or improved bone quality at all skeletal sites evaluated and did not cause any mineralization defects.
In an 8-week study in androgen-deficient orchiectomized (ORX) male rats, a male osteoporosis model, the effects of 5 and 25 mcg/kg/day abaloparatide (≥47-fold clinical exposures by AUC) were examined on bone formation, bone mass, and bone strength. Abaloparatide induced bone formation and improved cortical and trabecular BMD, geometry, and architecture without increasing parameters of bone resorption.
Clinical Studies
Efficacy Study In Women With Postmenopausal Osteoporosis
The efficacy of TYMLOS for the treatment of postmenopausal osteoporosis was evaluated in Study 003 (NCT 01343004), an 18-month, randomized, multicenter, double-blind, placebocontrolled clinical trial in postmenopausal women aged 49 to 86 years (mean age of 69) who were randomized to receive TYMLOS 80 mcg (N = 824) or placebo (N = 821) given subcutaneously once daily. Approximately 80% of patients were Caucasian, 16% were Asian, and 3% were Black; 24% were Hispanic. At baseline, the mean T-scores were -2.9 at the lumbar spine, -2.1 at the femoral neck, and -1.9 at the total hip. At baseline, 24% of patients had at least one prevalent vertebral fracture and 48% had at least one prior nonvertebral fracture. Patients took daily supplemental calcium (500 to 1000 mg) and vitamin D (400 to 800 IU).
The efficacy study was extended as Study 005 (NCT 01657162), an open-label study where patients were no longer receiving TYMLOS or placebo but were maintained in their original randomized treatment group and received 70 mg alendronate weekly, with calcium and vitamin D supplements for 6 months. Study 005 enrolled 1139 patients, representing 92% of patients who completed Study 003. This included 558 patients who had previously received TYMLOS and 581 patients who had previously received placebo. The cumulative 25-month efficacy dataset included 18 months of exposure to TYMLOS or placebo in Study 003, 1 month of no treatment, followed by 6 months of alendronate therapy in Study 005. Study 005 was then continued to complete 18 months of additional alendronate exposure during which time patients were no longer blinded to their original Study 003 treatment group.
Effect On New Vertebral Fractures
The primary endpoint was the incidence of new vertebral fractures in patients treated with TYMLOS compared to placebo. TYMLOS resulted in a significant reduction in the incidence of new vertebral fractures compared to placebo at 18 months (0.6% TYMLOS compared to 4.2% placebo, p <0.0001). The absolute risk reduction in new vertebral fractures was 3.6% at 18 months and the relative risk reduction was 86% for TYMLOS compared to placebo (Table 3). The incidence of new vertebral fractures at 25 months was 0.6% in patients treated with TYMLOS then alendronate, compared to 4.4% in patients treated with placebo then alendronate (p <0.0001). The relative risk reduction in new vertebral fractures at 25 months was 87% for patients treated with TYMLOS then alendronate, compared to patients treated with placebo then alendronate, and the absolute risk reduction was 3.9% (Table 3). After 24 months of open-label alendronate therapy, the vertebral fracture risk reduction achieved with TYMLOS therapy was maintained.
Table 3: Percentage of Postmenopausal Women with Osteoporosis with New Vertebral Fractures (modified Intent to Treat Population*†
|
Percentage of Postmenopausal Women With Fractures |
Absolute Risk Reduction (%)
(95% CI‡) |
Relative Risk Reduction (%)(95% CI‡) |
|
TYMLOS )
(N=690*)
(%) |
Placebo
(N=711*)
(%) |
| 0-18 months |
0.6 |
4.2 |
3.6
(2.1, 5.4) |
86
(61, 95) |
|
TYMLOS/
Alendronate
(N=544†)
(%) |
Placebo/
Alendronate
(N=568†)
(%) |
|
|
| 0-25 months |
0.6 |
4.4 |
3.9
(2.1, 5.9) |
87
(59, 96) |
* Includes patients who had both pre- and post-treatment spine radiographs in Study 003
† Includes patients who had both pre- and post-treatment spine radiographs in Study 005
‡ Confidence Interval |
Effect On Nonvertebral Fractures
TYMLOS resulted in a significant reduction in the incidence of nonvertebral fractures at the end of the 18 months of treatment plus 1 month follow-up where no drug was administered (2.7% for TYMLOS-treated patients compared to 4.7% for placebo-treated patients). The relative risk reduction in nonvertebral fractures for TYMLOS compared to placebo was 43% (logrank test p = 0.049) and the absolute risk reduction was 2.0%.
Following 6 months of alendronate treatment in Study 005, the cumulative incidence of nonvertebral fractures at 25 months was 2.7% for women in the prior TYMLOS group compared to 5.6% for women in the prior placebo group (Figure 1). At 25 months, the relative risk reduction in nonvertebral fractures was 52% (logrank test p = 0.017) and the absolute risk reduction was 2.9%.
Figure 1: Cumulative Incidence of Nonvertebral Fractures* over 25 Months (Intent to Treat Population)†
 |
* Excludes fractures of the sternum, patella, toes, fingers, skull and face and those associated with high trauma.
† Includes patients randomized in Study 003 |
TYMLOS demonstrated consistent reductions in the risk of vertebral and nonvertebral fractures regardless of age, years since menopause, presence or absence of prior fracture (vertebral, nonvertebral), and BMD at baseline.
Effect On Bone Mineral Density (BMD)
Treatment with TYMLOS for 18 months in Study 003 resulted in significant increases in BMD compared to placebo at the lumbar spine, total hip, and femoral neck, each with p<0.0001 (Table 4). Similar findings were seen following 6 months of alendronate treatment in Study 005 (Table 4).
Table 4: Mean Percent Changes in Bone Mineral Density (BMD) From Baseline to Endpoint in Postmenopausal Women with Osteoporosis (Intent to Treat Population)*†‡
|
TYMLOS
(N=824*)
(%) |
Placebo
(N=821*)
(%) |
Treatment Difference
(%)
(95% CI§) |
| 18 Months |
| Lumbar Spine |
9.2 |
0.5 |
8.8 (8.2, 9.3) |
| Total Hip |
3.4 |
-0.1 |
3.5 (3.3, 3.8) |
| Femoral Neck |
2.9 |
-0.4 |
3.3 (3.0, 3.7) |
|
TYMLOS/
Alendronate
(N=558†)
(%) |
Placebo/
Alendronate
(N=581†)
(%) |
|
| 25 Months |
| Lumbar Spine |
12.8 |
3.5 |
9.3 (8.6, 10.1) |
| Total Hip |
5.5 |
1.4 |
4.1 (3.7, 4.5) |
| Femoral Neck |
4.5 |
0.5 |
4.1 (3.6, 4.6) |
* Includes patients randomized in Study 003
† Includes patients enrolled in Study 005
‡ Last-observation-carried-forward
§ Confidence Interval |
There was no evidence of differences in the effects of TYMLOS on BMD across subgroups defined by age, years since menopause, race, ethnicity, geographic region, presence or absence of prior fracture (vertebral, nonvertebral), and BMD at baseline.
Effect On Bone Histology
Bone biopsy specimens were obtained from 71 patients with osteoporosis after 12 – 18 months of treatment (36 in the TYMLOS group and 35 in the placebo group). Of the biopsies obtained, 55 were adequate for quantitative histomorphometry assessment (27 in the TYMLOS group and 28 in the placebo group). Qualitative and quantitative histology assessment showed normal bone architecture and no evidence of woven bone, marrow fibrosis, or mineralization defects.
Men With Osteoporosis
The efficacy of TYMLOS for the treatment of men with osteoporosis was evaluated in Study 019 (NCT 03512262), a 12-month, randomized, multicenter, double-blind, placebo-controlled clinical trial in men aged 42 to 85 years (mean age of 68) who were randomized to receive TYMLOS 80 mcg (N = 149) or placebo (N = 79) given subcutaneously once daily. Approximately 95% of patients were Caucasian, 4% were Asian, and <1% (0.4%) were Black; 16% were Hispanic. At baseline, the mean T-scores were -2.1 at the lumbar spine, -2.1 at the femoral neck, and -1.7 at the total hip. Patients took daily supplemental calcium (500 to 1000 mg) and vitamin D (400 to 800 IU).
Effect On Bone Mineral Density (BMD)
The primary endpoint was the percent change from baseline in lumbar spine BMD at 12 months in patients treated with TYMLOS compared to placebo. Treatment with TYMLOS for 12 months in Study 019 resulted in significant increases in BMD compared to placebo at the lumbar spine, total hip, and femoral neck, each with p<0.0001 (Table 5).
Table 5: Mean Percent Changes in Bone Mineral Density (BMD) From Baseline to 12 Months in Men with Osteoporosis (Intent to Treat Population)
|
TYMLOS
(N=149*)
(%) |
Placebo
(N=79*)
(%) |
Treatment Difference
(%)
(99% CI†) |
| 12 Months |
| Lumbar Spine |
8.5 |
1.2 |
7.3 (5.1, 9.6) |
| Total Hip |
2.1 |
<0.1 |
2.1 (1.0, 3.2) |
| Femoral Neck |
3.0 |
0.2 |
2.8 (1.4, 4.2) |
* Includes patients randomized in Study 019
† Confidence Interval |
There was no evidence of differences in the effects of TYMLOS on BMD at Month 12 across subgroups defined by age, race, ethnicity, geographic region, presence or absence of prior fracture, and BMD at baseline.