Stroke

In the clinical trials for OSPHENA (duration of treatment up to 15 months), the incidence rates of thromboembolic and hemorrhagic stroke were 1.13 and 3.39 per thousand women years, respectively in OSPHENA 60 mg treatment group and 3.15 and 0 per thousand women years in placebo.

Should thromboembolic or hemorrhagic stroke occur or be suspected, OSPHENA should be discontinued immediately.

In the WHI estrogen-alone substudy, a statistically significant increased risk of stroke was reported in women 50 to 79 years of age receiving daily CE (0.625 mg)-alone compared to women in the same age group receiving placebo (45 versus 33 per ten thousand women years). The increase in risk was demonstrated in year 1 and persisted.

Coronary Heart Disease

In the OSPHENA clinical trials, two cases of myocardial infarction (MI) occurred in women receiving 60 mg of ospemifene.

In the WHI estrogen-alone substudy, no overall effect on coronary heart disease (CHD) events (defined as nonfatal MI, silent MI, or CHD death) was reported in women receiving estrogen-alone compared to placebo.

Venous Thromboembolism

In the OSPHENA clinical trials, two cases of DVT occurred in women receiving OSPHENA 60 mg. Should a VTE occur or be suspected, OSPHENA should be discontinued immediately.

If feasible, OSPHENA should be discontinued at least 4 to 6 weeks before surgery of the type associated with an increased risk of thromboembolism, or during periods of prolonged immobilization.

In the WHI estrogen-alone substudy, the risk of VTE (DVT and PE) was increased for women receiving daily CE (0.625 mg)-alone compared to placebo (30 versus 22 per ten thousand women years), although only the increased risk of DVT reached statistical significance (23 versus 15 per ten thousand women years). The increase in VTE risk was demonstrated during the first 2 years.

Endometrial Cancer

OSPHENA is an estrogen agonist/antagonist with tissue selective effects. In the endometrium, OSPHENA has agonistic effects. In the OSPHENA clinical trials (60 mg treatment group), no cases of endometrial cancer were seen with exposure up to 52 weeks. There was a single case of simple hyperplasia without atypia. Endometrial thickening equal to 5 mm or greater was seen in the OSPHENA up to 52 weeks treatment groups at a rate of 101.4 per thousand women vs. 20.9 per thousand women for placebo. The incidence of any type of proliferative (weakly plus active plus disordered) endometrium was 26.3 per thousand women in the OSPHENA up to 52 weeks treatment groups vs. 0 per thousand women for placebo. Uterine polyps occurred at an incidence of 19.6 per thousand women in the OSPHENA up to 52 weeks treatment groups vs. 8.3 per thousand women for placebo.

An increased risk of endometrial cancer has been reported with the use of unopposed estrogen therapy in a woman with a uterus. The reported endometrial cancer risk among unopposed estrogen users is about 2 to 12 times greater than in non-users, and appears dependent on duration of treatment and on estrogen dose. Most studies show no significant increased risk associated with the use of estrogens for less than 1 year. The greatest risk appears to be associated with prolonged use, with increased risks of 15- to 24-fold for 5 to 10 years or more. This risk has been shown to persist for at least 8 to 15 years after estrogen therapy is discontinued. Adding a progestin to postmenopausal estrogen therapy has been shown to reduce the risk of endometrial hyperplasia, which may be a precursor to endometrial cancer. There are, however, possible risks that may be associated with the use of progestins with estrogens compared to estrogen-alone regimens. These include an increased risk of breast cancer. The use of progestins with OSPHENA therapy was not evaluated in the clinical trials.

Clinical surveillance of all women using OSPHENA is important. Adequate diagnostic measures, including directed or random endometrial sampling when indicated, should be undertaken to rule out malignancy in postmenopausal women with undiagnosed persistent or recurring abnormal genital bleeding.

Breast Cancer

OSPHENA 60 mg has not been adequately studied in women with breast cancer; therefore, it should not be used in women with known or suspected breast cancer.

Risk Summary

Data

Risk Summary

It is not known whether OSPHENA is excreted in human breast milk. There are no data on the effects of OSPHENA on the breastfed child or the effects on milk production. Do not breastfeed while taking OSPHENA. Ospemifene was excreted in rat milk [see Data].

Data

In a nonclinical study, ospemifene was excreted in rat milk and detected at concentrations higher than that in maternal plasma.

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.

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 (2.1)].

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

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.

Carcinogenesis

In a 2-year carcinogenicity study in female mice, ospemifene was orally administered at 100, 400, or 1500 mg/kg/day. No evaluation for carcinogenicity was conducted in male mice. There was significant increase in adrenal subcapsular cell adenomas at 4 and 5 times the human exposure based on AUC, and adrenal cortical tumors at 5 times the human exposure. In the ovary, an increase in sex cord/stromal tumors, tubulostromal tumors, granulosa cell tumors, and luteomas was also seen. These findings occurred at doses 2 to 5 times the human exposure based on AUC and are probably related to estrogenic/antiestrogenic effect of ospemifene in mice.

In a 2-year carcinogenicity study in rats, ospemifene was orally administered at 10, 50, or 300 mg/kg/day. A significant increase in thymomas was recorded for males and thymomas for females at all ospemifene dose levels, or 0.3 to 1.2 times the human exposure based on AUC. In the liver, an increase in hepatocellular tumors was recorded for females at all ospemifene dose levels.

Mutagenesis

Ospemifene was not genotoxic in vitro in the Ames test in strains of Salmonella typhimurium or at the thymidine kinase (tk) locus of mouse lymphoma L5178Y cells in the absence and in the presence of a metabolic activator system. In in vivo testing, ospemifene was not genotoxic in a standard mouse bone marrow micronucleus test or in a determination of DNA adducts in the liver of rats.

Impairment of Fertility

The effect of ospemifene on fertility was not directly evaluated. In female rats and monkeys, decreases in ovarian and uterine weights, decreased corpora lutea number, increased ovarian cysts, uterine atrophy, and disrupted cycles were observed when given repeated daily oral doses. In male rats, atrophy of the prostate and seminal vesicles was noted. The effects on reproductive organs observed in animals are consistent with the estrogen receptor activity of ospemifene and potential for impairment of fertility.