CLINICAL PHARMACOLOGY
Mechanism Of Action
OSPHENA is an estrogen receptor agonist/antagonist with tissue selective effects. Its biological actions are mediated through binding to estrogen receptors. This binding results in activation of estrogenic pathways in some tissues (agonism) and blockade of estrogenic pathways in others (antagonism).
Pharmacokinetics
Absorption
Following a single oral administration of OSPHENA 60 mg tablet in postmenopausal women under fasted condition, peak median serum concentration was reached at approximately 2 hours (range: 1 to 8 hours) post-dose (see Figure 2). Mean ospemifene Cmax and AUC0-inf were 533 ng/mL and 4165 ng•hr/mL, respectively. After a single oral administration of OSPHENA 60 mg tablet in postmenopausal women with a high fat/high calorie (860 kcal) meal, Cmax was reached at approximately 2.5 hours (range: 1 to 6 hours) post-dose. Mean ospemifene Cmax and AUC0-inf were 1198 ng/mL and 7521 ng•hr/mL, respectively. The absolute bioavailability of ospemifene was not evaluated. Ospemifene exhibits less than dose-proportional pharmacokinetics from 25 to 200 mg with ospemifene capsule formulation. Accumulation of ospemifene with respect to AUC0-inf was
approximately 2 after twelve weeks of daily administration. Steady-state was reached after nine days of ospemifene administration.
Figure 2: Mean Serum Concentration Profile of Ospemifene Following a Single Oral Administration of OSPHENA 60 mg Tablet in Postmenopausal Women Under Fed (N=28) and Fasted (N=91) Conditions
Food Effect
In general, food increased the bioavailability of ospemifene by approximately 2-3 fold. In a cross-study comparison, single dose OSPHENA 60 mg tablet administered with a high fat/high calorie meal (860 kcal) in postmenopausal women increased Cmax and AUC0-inf by 2.3- and 1.7-fold, respectively, compared to fasted condition. Elimination half-life and time to maximum concentration (Tmax) were unchanged in the presence of food. In two food effect studies in healthy males using different ospemifene tablet formulations, Cmax and AUC0-inf increased by 2.3- and 1.8-fold, respectively, with a low fat/low calorie meal (300 kcal) and increased by 3.6- and 2.7-fold, respectively, with a high fat/high calorie meal (860 kcal), compared to fasted condition. OSPHENA should be taken with food [see DOSAGE AND ADMINISTRATION].
Distribution
OSPHENA is highly (>99 percent) bound to serum proteins. The apparent volume of distribution is 448 L.
Metabolism
In vitro experiments with human liver microsomes indicated that ospemifene primarily undergoes metabolism via CYP3A4, CYP2C9, and CYP2C19. The major metabolite was 4-hydroxyospemifene. The apparent total body clearance is 9.16 L/hr using a population approach.
Excretion
The apparent terminal half-life of ospemifene in postmenopausal women is approximately 26 hours. Following an oral administration of ospemifene, approximately 75% and 7% of the dose were excreted in feces and urine, respectively. Less than 0.2% of the ospemifene dose was excreted unchanged in urine.
Use In Specific Populations
Pediatric
The pharmacokinetics of ospemifene in pediatric patients has not been evaluated [see Use In Specific Populations].
Geriatric
No differences in ospemifene pharmacokinetics were detected with regard to age (range 40 to 80 years) [see Use In Specific Populations].
Race
Race did not have a clinically relevant effect on ospemifene pharmacokinetics.
Renal Impairment
In women with severe renal impairment (CrCL <30 mL/min), the Cmax and AUC0-inf for ospemifene following a single 60 mg dose administered with a high fat/high calorie meal were lower by 21% and higher by 20%, respectively [see Use In Specific Populations].
Hepatic Impairment
In women with mild hepatic impairment (Child-Pugh Class A), the Cmax and AUC0-inf for ospemifene following a single 60 mg dose administered with a high fat/high calorie meal were lower by 21% and 9.1%, respectively, compared to women with normal hepatic function. In women with moderate hepatic impairment (Child-Pugh Class B), the Cmax and AUC0-inf for ospemifene following a single 60 mg dose administered with a high fat/high calorie meal were higher by 1% and 29%, respectively, compared to women with normal hepatic function. The effect of severe hepatic impairment on the pharmacokinetics of ospemifene has not been evaluated [see WARNINGS AND PRECAUTIONS, and Use In Specific Populations].
Drug Interactions
Ospemifene is metabolized primarily by CYP3A4 and CYP2C9. CYP2C19 and other pathways contribute to the metabolism of ospemifene. In order of decreasing potency, ospemifene was suggested to be a weak inhibitor for CYP2B6, CYP2C9, CYP2C19, CYP2C8, CYP2D6, and CYP3A4 in in vitro studies. Ospemifene is not a significant P-glycoprotein substrate in vitro; no in vivo transporter study was conducted.
Effect Of Co-Administered Drugs On The Pharmacokinetics Of Ospemifene
Fluconazole (CYP3A4/CYP2C9/CYP2C19 Inhibitor)
Fluconazole (a moderate CYP3A / strong CYP2C9 / moderate CYP2C19 inhibitor) 400 mg was given on Day 1 followed by 200 mg on Days 2 to 5 under fasted condition. On Day 5 approximately one hour after fluconazole administration, ospemifene 60 mg was administered after breakfast (two slices of bread with ham, cheese, a few slices of cucumber and/or tomatoes, and juice). Fluconazole 200 mg was taken for three additional days under fasted condition. Multiple doses of fluconazole in fourteen postmenopausal women increased the Cmax and AUC0-inf of ospemifene by 1.7- and 2.7-fold, respectively [see DRUG INTERACTIONS].
Rifampin (CYP3A4/CYP2C9/CYP2C19 Inducer)
Rifampin 600 mg was given once daily for 5 consecutive days (given at least one hour before or two hours after a meal) in the late afternoon. On Day 6 after an overnight fast, ospemifene 60 mg was administered in the morning after under fed condition (two slices of bread with ham, cheese, a few slices of cucumber and/or tomatoes, and juice). Multiple doses of rifampin 600 mg in twelve postmenopausal women reduced Cmax and AUC0-inf of ospemifene by 51% and 58%, respectively. Rifampin and other inducers of CYP3A4 are expected to decrease the systemic exposure of ospemifene [see DRUG INTERACTIONS].
Ketoconazole (CYP3A4 Inhibitor)
Ketoconazole 400 mg was given once daily for 4 consecutive days after breakfast. On Day 5 after an overnight fast, ketoconazole 400 mg and ospemifene 60 mg were co-administered under fed condition (two slices of bread with ham, cheese, a few slices of cucumber and/or tomatoes, and juice). Ketoconazole administration once daily continued for an additional 3 days (Days 6 to 8). Co-administration of a single 60 mg dose of ospemifene and multiple doses of ketoconazole in twelve postmenopausal women increased Cmax and AUC0-inf by 1.5- and 1.4-fold, respectively [see DRUG INTERACTIONS].
Omeprazole (CYP2C19 Inhibitor)
Omeprazole (a moderate CYP2C19 inhibitor) 40 mg was given for 5 days. On Day 5, approximately one hour after omeprazole administration, ospemifene 60 mg was administered after breakfast (two slices of bread with ham, cheese, a few slices of cucumber and/or tomatoes, and juice). Multiple doses of omeprazole in fourteen postmenopausal women increased Cmax and AUC0-inf by 1.20- and 1.17-fold, respectively.
Effect Of Ospemifene On The Pharmacokinetics Of The Co-Administered Drug
Warfarin
Ospemifene 60 mg was given after a light breakfast (two slices of bread with ham and cheese, and juice) once daily for 12 days in sixteen postmenopausal women who were determined to be rapid metabolizers of CYP2C9 (CYP2C9*1/*1 or CYP2C9*1/*2). On Day 8, a single dose of warfarin 10 mg and vitamin K 10 mg were administered one hour after a light breakfast. The geometric mean ratio (90% CI) for S-warfarin with and without ospemifene for Cmax and AUC0-inf were 0.97 (0.92-1.02) and 0.96 (0.91-1.02), respectively. Multiple doses of ospemifene did not significantly affect the pharmacokinetics of a single dose of warfarin. No study was conducted with multiple doses of warfarin.
Omeprazole
Ospemifene 60 mg was administered once daily for 7 days after a light meal in the late afternoon in fourteen postmenopausal women. On Day 8 after an overnight fast, a single 20 mg dose of omeprazole was administered in the morning of at least 10 hrs; ospemifene was not given on Day 8. The geometric mean ratio for the metabolic index (omeprazole/5-hydroxyomeprazole) at the concentration at the 3 hr time point and for AUC0-8hr was 0.97 with and without ospemifene. It is unclear if ospemifene will affect the pharmacokinetics of drugs metabolized by CYP2C19 due to the significant time gap between ospemifene and omeprazole administration.
Bupropion
Ospemifene 60 mg was administered once daily for seven consecutive days after the evening meal in sixteen postmenopausal women (not homozygous for CYP2B6*6). On Day 8 after an overnight fast, a single 150 mg dose of sustained release bupropion was administered in morning under fasted condition. The geometric mean ratio (90% CI) for bupropion with and without ospemifene for Cmax and AUC0-inf were 0.82 (0.75-0.91) and 0.81 (0.77-0.86), respectively. The geometric mean ratio (90% CI) for hydroxybupropion, an active metabolite formed via CYP2B6, with and without ospemifene for Cmax and AUC0-inf were 1.16 (1.09-1.24) and 0.98 (0.92-1.04), respectively.
Midazolam
Ospemifene 60 mg was administered once daily for 14 days in fifteen postmenopausal women. On Day 14, a single 5 mg dose of midazolam (a CYP3A4 substrate) was administered. All doses of midazolam and ospemifene were administered in morning in the fed state (i.e., after a standard breakfast and at the same time every day). The geometric mean ratio (90% CI) for midazolam with and without ospemifene for Cmax and AUC0-inf were 1.05 (0.95-1.16) and 0.87 (0.82-0.92), respectively.
Clinical Studies
The effectiveness and safety of OSPHENA on moderate to severe symptoms of vulvar and vaginal atrophy in postmenopausal women were examined in four placebo-controlled clinical trials (three 12-week efficacy trials and one 52-week long-term safety trial). In the four placebo-controlled trials, a total of 1100 women received placebo and 1416 women received 60 mg OSPHENA.
Trial 1 was a 12-week, randomized, double-blind, placebo-controlled, parallel-group trial that enrolled 826 generally healthy postmenopausal women between 41 to 81 years of age (mean 59 years of age) who at baseline had ≤5 percent superficial cells on a vaginal smear, a vaginal pH >5.0, and who identified at least one moderate to severe vaginal symptom that was considered the most bothersome to her (vaginal dryness, pain during intercourse [dyspareunia], or vaginal irritation/itching). Treatment groups included 30 mg ospemifene (n=282), 60 mg ospemifene (n=276), and placebo (n=268). All women were assessed for improvement in the mean change from baseline to Week 12 for the co-primary efficacy variables of: most bothersome symptom (MBS) of vulvar and vaginal atrophy (defined as the individual moderate to severe symptom that was identified by the woman as most bothersome at baseline), percentage of vaginal superficial and vaginal parabasal cells on a vaginal smear, and vaginal pH. Following completion of 12-weeks, women with an intact uterus were allowed to enroll in a 40-week double-blind extension study, and women without an intact uterus were allowed to enroll in a 52-week open-label extension study.
Trial 2 was a 12-week, randomized, double-blind, placebo-controlled, parallel-group trial that enrolled 919 generally healthy postmenopausal women between 41 to 79 years of age (mean 59 years of age) who at baseline had ≤5 percent superficial cells on a vaginal smear, a vaginal pH >5.0, and who identified either moderate to severe vaginal dryness (dryness cohort) or moderate to severe dyspareunia (dyspareunia cohort) as most bothersome to her at baseline. Treatment groups included 60 mg ospemifene (n=463) and placebo (n=456). Primary endpoints and study conduct were similar to those in Trial 1.
Trial 3 was a 12-week, randomized, double-blind, placebo-controlled, parallel-group trial that enrolled 631 generally healthy postmenopausal women between 40 and 80 years of age (mean 60 years of age) who at baseline had ≤5 percent superficial cells on a vaginal smear, a vaginal pH >5.0, and had moderate to severe vaginal dryness as the self-reported most bothersome symptom of VVA. Treatment groups included 60 mg ospemifene (n=316) and placebo (n=315). Primary endpoints and study conduct were similar to those in Trials 1 and 2. In Trial 3, 52 healthy postmenopausal women in the 60 mg ospemifene treatment group and 53 in placebo received treatment for up to 52-weeks.
Trial 4 was a 52-week, randomized, double-blind, placebo-controlled, long-term safety trial that enrolled 426 generally healthy postmenopausal women between 49 to 79 years of age (mean 62 years of age) with an intact uterus. Treatment groups included 60 mg ospemifene (n=363) and placebo (n=63).
Effects On Dyspareunia
In Trials 1 and 2, the modified intent-to-treat population of women treated with ospemifene when compared to placebo demonstrated a statistically significant improvement (least square mean change from baseline to Week 12) in the moderate to severe most bothersome symptom of dyspareunia (Trial 1, p=0.0012 and Trial 2, p<0.0001). See Table 3. A statistically significant increase in the proportion of superficial cells and a corresponding statistically significant decrease in the proportion of parabasal cells on a vaginal smear were also demonstrated (p<0.0001 for both trials). The mean reduction in vaginal pH between baseline and Week 12 was also statistically significant (p<0.0001 for both trials).
Table 3: Week 12 Effects on Dyspareunia (the Woman’s Self-Identified Most Bothersome Moderate to Severe Symptom of Vulvar and Vaginal Atrophy at Baseline). Mean Change in Severity at Week 12 with Last Observation Carried Forward (LOCF), Modified Intent-to-Treat Populationa
Trial 1 Results |
Most Bothersome Moderate to Severe Symptom at Baseline |
OSPHENA (ospemifene) 60 mg
(N=110) |
Placebo
(N=113) |
Dyspareunia |
Baseline Mean (SD) |
2.7 (0.44) |
2.7 (0.45) |
LS Mean Change from Baseline (SE) |
-1.4 (0.11) |
-0.9 (0.11) |
p-value vs. placebob |
0.0012 |
- |
Trial 2 Results |
Most Bothersome Moderate to Severe Symptom at Baseline |
OSPHENA (ospemifene) 60 mg
(N=301) |
Placebo
(N=297) |
Dyspareunia |
Baseline Mean (SD) |
2.7 (0.47) |
2.7 (0.47) |
LS Mean Change from Baseline (SE) |
-1.5 (0.06) |
-1.2 (0.07) |
p-value vs. placebob |
<0.0001 |
- |
a. The modified intent-to-treat population (mITT) included only women in the ITT population who at baseline met the inclusion criteria of ≤5 percent superficial cells on a vaginal smear, a vaginal pH > 5.0, and who identified moderate or severe dyspareunia as the most bothersome vaginal symptom.
b. p-values for dyspareunia were computed using Cochran-Mantel-Haenszel method controlling for study center and uterus status (presence or absence; only in Trial 1).
Definitions: ITT = intent-to-treat; LOCF = last observation carried forward; SD = standard deviation; SE = standard error; LS = least square |
Effects On Vaginal Dryness
All three trials evaluated the most bothersome symptom of vaginal dryness. Trial 2 did not demonstrate a statistically significant improvement in the moderate to severe most bothersome symptom of vaginal dryness. In Trials 1 and 3, the modified intent-to-treat population of women treated with ospemifene when compared to placebo demonstrated a statistically significant improvement in the moderate to severe most bothersome symptom of vaginal dryness (Trial 1, p=0.0136 and Trial 3, p<0.0001). See Table 4. A statistically significant increase in the proportion of superficial cells and a corresponding statistically significant decrease in the proportion of parabasal cells on a vaginal smear were also demonstrated (p<0.0001 for both trials). The mean reduction in vaginal pH between baseline and Week 12 was also statistically significant (p<0.0001 for both trials).
Table 4: Week 12 Effects on Vaginal Dryness (the Woman’s Self-Identified Most Bothersome Moderate to Severe Symptom of Vulvar and Vaginal Atrophy at Baseline). Change in Severity at Week 12, Modified Intent-to-Treat Populationa
Trial 1 Results |
Most Bothersome Moderate to Severe Symptom at Baseline |
OSPHENA (ospemifene) 60 mg
(N=113) |
Placebo
(N=104) |
Vaginal Dryness |
Baseline Mean (SD) |
2.5 (0.50) |
2.4 (0.49) |
LS Mean Change from Baseline (SE) |
-1.3 (0.09) |
-0.9 (0.10) |
p-value vs. placebob |
0.0136 |
- |
Trial 3 Results |
Most Bothersome Moderate to Severe Symptom at Baseline |
OSPHENA (ospemifene) 60 mg
(N=269) |
Placebo
(N=263) |
Vaginal Dryness |
Baseline Mean (SD) |
2.6 (0.50) |
2.6 (0.50) |
Change from Baseline (SD) |
-1.3 (1.00) |
-0.9 (0.95) |
p-value vs. placebob |
< 0.0001 |
- |
a. The modified intent-to-treat population (mITT) included only women in the ITT population who at baseline met the inclusion criteria of ≤5 percent superficial cells on a vaginal smear, a vaginal pH > 5.0, and who identified moderate or severe dyspareunia as the most bothersome vaginal symptom.
b. p-value for vaginal dryness in Trial 1 was computed using Cochran-Mantel-Haenszel method controlling for study center and uterus status (presence or absence), and using LOCF. P-value for vaginal dryness in Trial 3 was computed using a GEE model with terms for treatment group, time, treatment-by-time and study center as fixed effects and baseline value as covariate.
Definitions: ITT = intent-to-treat; LOCF = last observation carried forward; GEE = generalized estimated equations; SD = standard deviation; SE = standard error; LS = least square |