DESCRIPTION SECTION

11 DESCRIPTION

Exemestane Tablets, USP for oral administration contain 25 mg of exemestane, an irreversible, steroidal aromatase inactivator. Exemestane is chemically described as 6-methylenandrosta-1,4-diene-3,17-dione. Its molecular formula is C20 H24 O2 and its structural formula is as follows:

The active ingredient is a white to slightly yellow crystalline powder with a molecular weight of 296.41. Exemestane is freely soluble in N, N-dimethylformamide, soluble in methanol, and practically insoluble in water.

Each Exemestane Tablet, USP contains the following inactive ingredients: colloidal silicon dioxide, crospovidone, hydroxypropyl methylcellulose, magnesium stearate, mannitol, microcrystalline cellulose, polysorbate 80, sodium starch glycolate. The tablet coating contains: hypromellose, propylene glycol, and titanium dioxide.

CLINICAL PHARMACOLOGY SECTION

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Breast cancer cell growth may be estrogen-dependent. Aromatase is the principal enzyme that converts androgens to estrogens both in pre- and postmenopausal women. While the main source of estrogen (primarily estradiol) is the ovary in premenopausal women, the principal source of circulating estrogens in postmenopausal women is from conversion of adrenal and ovarian androgens (androstenedione and testosterone) to estrogens (estrone and estradiol) by the aromatase enzyme in peripheral tissues.

Exemestane is an irreversible, steroidal aromatase inactivator, structurally related to the natural substrate androstenedione. It acts as a false substrate for the aromatase enzyme, and is processed to an intermediate that binds irreversibly to the active site of the enzyme, causing its inactivation, an effect also known as "suicide inhibition." Exemestane significantly lowers circulating estrogen concentrations in postmenopausal women, but has no detectable effect on adrenal biosynthesis of corticosteroids or aldosterone. Exemestane has no effect on other enzymes involved in the steroidogenic pathway up to a concentration at least 600 times higher than that inhibiting the aromatase enzyme.

12.2 Pharmacodynamics

Effect on Estrogens

Multiple doses of exemestane ranging from 0.5 to 600 mg/day were administered to postmenopausal women with advanced breast cancer. Plasma estrogen (estradiol, estrone, and estrone sulfate) suppression was seen starting at a 5-mg daily dose of exemestane, with a maximum suppression of at least 85% to 95% achieved at a 25-mg dose. Exemestane 25 mg daily reduced whole body aromatization (as measured by injecting radiolabeled androstenedione) by 98% in postmenopausal women with breast cancer. After a single dose of exemestane 25 mg, the maximal suppression of circulating estrogens occurred 2 to 3 days after dosing and persisted for 4 to 5 days.

Effect on Corticosteroids

In multiple-dose trials of doses up to 200 mg daily, exemestane selectivity was assessed by examining its effect on adrenal steroids. Exemestane did not affect cortisol or aldosterone secretion at baseline or in response to ACTH at any dose. Thus, no glucocorticoid or mineralocorticoid replacement therapy is necessary with exemestane treatment.

Other Endocrine Effects

Exemestane does not bind significantly to steroidal receptors, except for a slight affinity for the androgen receptor (0.28% relative to dihydrotestosterone). The binding affinity of its 17-dihydrometabolite for the androgen receptor, however, is 100 times that of the parent compound. Daily doses of exemestane up to 25 mg had no significant effect on circulating levels of androstenedione, dehydroepiandrosterone sulfate, or 17-hydroxyprogesterone, and were associated with small decreases in circulating levels of testosterone. Increases in testosterone and androstenedione levels have been observed at daily doses of 200 mg or more. A dose-dependent decrease in sex hormone binding globulin (SHBG) has been observed with daily exemestane doses of 2.5 mg or higher. Slight, nondose- dependent increases in serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels have been observed even at low doses as a consequence of feedback at the pituitary level. Exemestane 25 mg daily had no significant effect on thyroid function [free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH)].

Coagulation and Lipid Effects

In study 027 of postmenopausal women with early breast cancer treated with exemestane (N=73) or placebo (N=73), there was no change in the coagulation parameters activated partial thromboplastin time [APTT], prothrombin time [PT], and fibrinogen. Plasma HDL cholesterol was decreased 6–9% in exemestane treated patients; total cholesterol, LDL cholesterol, triglycerides, apolipoprotein-A1, apolipoprotein-B, and lipoprotein-a were unchanged. An 18% increase in homocysteine levels was also observed in exemestane treated patients compared with a 12% increase seen with placebo.

12.3 Pharmacokinetics

Following oral administration to healthy postmenopausal women, plasma concentrations of exemestane decline polyexponentially with a mean terminal half-life of about 24 hours. The pharmacokinetics of exemestane are dose proportional after single (10 to 200 mg) or repeated oral doses (0.5 to 50 mg). Following repeated daily doses of exemestane 25 mg, plasma concentrations of unchanged drug are similar to levels measured after a single dose. Pharmacokinetic parameters in postmenopausal women with advanced breast cancer following single or repeated doses have been compared with those in healthy, postmenopausal women. After repeated dosing, the average oral clearance in women with advanced breast cancer was 45% lower than the oral clearance in healthy postmenopausal women, with corresponding higher systemic exposure. Mean AUC values following repeated doses in women with breast cancer (75.4 ng•h/mL) were about twice those in healthy women (41.4 ng•h/mL).

Absorption

Following oral administration, exemestane appeared to be absorbed more rapidly in women with breast cancer than in the healthy women, with a mean tmax of 1.2 hours in the women with breast cancer and 2.9 hours in healthy women. Approximately 42% of radiolabeled exemestane was absorbed from the gastrointestinal tract. A high-fat breakfast increased AUC and Cmax of exemestane by 59% and 39%, respectively, compared to fasted state.

Distribution

Exemestane is distributed extensively into tissues. Exemestane is 90% bound to plasma proteins and the fraction bound is independent of the total concentration. Albumin and α1 1-acid glycoprotein both contribute to the binding. The distribution of exemestane and its metabolites into blood cells is negligible.

Metabolism

Exemestane is extensively metabolized, with levels of the unchanged drug in plasma accounting for less than 10% of the total radioactivity. The initial steps in the metabolism of exemestane are oxidation of the methylene group in position 6 and reduction of the 17-keto group with subsequent formation of many secondary metabolites. Each metabolite accounts only for a limited amount of drug-related material. The metabolites are inactive or inhibit aromatase with decreased potency compared with the parent drug. One metabolite may have androgenic activity [see Clinical Pharmacology (12.2)]. Studies using human liver preparations indicate that cytochrome P 450 3A4 (CYP 3A4) is the principal isoenzyme involved in the oxidation of exemestane. Exemestane is metabolized also by aldoketoreductases.

Elimination

Following administration of radiolabeled exemestane to healthy postmenopausal women, the cumulative amounts of radioactivity excreted in urine and feces were similar (42 ± 3% in urine and 42 ± 6% in feces over a 1-week collection period). The amount of drug excreted unchanged in urine was less than 1% of the dose.

Specific Populations

Geriatric: Healthy postmenopausal women aged 43 to 68 years were studied in the pharmacokinetic trials. Age- related alterations in exemestane pharmacokinetics were not seen over this age range.

Gender: The pharmacokinetics of exemestane following administration of a single, 25-mg tablet to fasted healthy males (mean age 32 years) were similar to the pharmacokinetics of exemestane in fasted healthy postmenopausal women (mean age 55 years).

Race: The influence of race on exemestane pharmacokinetics has not been evaluated.

Hepatic Impairment: The pharmacokinetics of exemestane have been investigated in subjects with moderate or severe hepatic impairment (Childs-Pugh B or C). Following a single 25-mg oral dose, the AUC of exemestane was approximately 3 times higher than that observed in healthy volunteers.

Renal Impairment: The AUC of exemestane after a single 25-mg dose was approximately 3 times higher in subjects with moderate or severe renal insufficiency (creatinine clearance <35 mL/min/1.73 m2) compared with the AUC in healthy volunteers.

Pediatric: The pharmacokinetics of exemestane have not been studied in pediatric patients.

Drug Interaction Studies

Exemestane does not inhibit any of the major CYP isoenzymes, including CYP 1A2, 2C9, 2D6, 2E1, and 3A4.

In a pharmacokinetic interaction study of 10 healthy postmenopausal volunteers pretreated with potent CYP 3A4 inducer rifampicin 600 mg daily for 14 days followed by a single dose of exemestane 25 mg, the mean plasma Cmax and AUC0-∞ of exemestane were decreased by 41% and 54%, respectively [see Dosage and Administration (2.2) and Drug Interactions (7)].

In a clinical pharmacokinetic study, coadministration of ketoconazole, a potent inhibitor of CYP 3A4, has no significant effect on exemestane pharmacokinetics. Although no other formal drug-drug interaction studies with inhibitors have been conducted, significant effects on exemestane clearance by CYP isoenzyme inhibitors appear unlikely.

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DOSAGE FORMS & STRENGTHS SECTION

Highlight: Tablets: 25 mg (3)

3 DOSAGE FORMS AND STRENGTHS

Exemestane Tablets, USP are white colored, round, biconvex, film-coated tablets debossed with "X" on one side and "1" on other side. Each tablet contains 25 mg of exemestane.

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CONTRAINDICATIONS SECTION

Highlight: Patients with a known hypersensitivity to the drug or to any of the excipients (4).

4 CONTRAINDICATIONS

Exemestane tablets are contraindicated in patients with a known hypersensitivity to the drug or to any of the excipients.

WARNINGS AND PRECAUTIONS SECTION

Highlight: * Reductions in bone mineral density (BMD) over time are seen with exemestane use (5.1).

• Routine assessment of 25-hydroxy vitamin D levels prior to the start of aromatase inhibitor treatment should be performed (5.2).
• Embryo-Fetal Toxicity: Can cause fetal harm. Advise females of reproductive potential of the potential risk to a fetus and to use effective contraception (5.6, 8.1, 8.3).

5 WARNINGS AND PRECAUTIONS

5.1 Reductions in Bone Mineral Density (BMD)

Reductions in bone mineral density (BMD) over time are seen with exemestane use. Table 1 describes changes in BMD from baseline to 24 months in patients receiving exemestane compared to patients receiving tamoxifen (IES) or placebo (027). Concomitant use of bisphosphonates, vitamin D supplementation, and calcium was not allowed.

Table 1. Percent Change in BMD from Baseline to 24 months, Exemestane vs. Control1

During adjuvant treatment with exemestane, women with osteoporosis or at risk of osteoporosis should have their bone mineral density formally assessed by bone densitometry at the commencement of treatment. Monitor patients for bone mineral density loss and treat as appropriate.

5.2 Vitamin D Assessment

Routine assessment of 25-hydroxy vitamin D levels prior to the start of aromatase inhibitor treatment should be performed, due to the high prevalence of vitamin D deficiency in women with early breast cancer (EBC). Women with vitamin D deficiency should receive supplementation with vitamin D.

5.3 Administration with Estrogen-Containing Agents

Exemestane tablets should not be coadministered with systemic estrogen- containing agents as these could interfere with its pharmacologic action.

5.4 Laboratory Abnormalities

In patients with early breast cancer, the incidence of hematological abnormalities of Common Toxicity Criteria (CTC) grade ≥1 was lower in the exemestane treatment group, compared with tamoxifen. Incidence of CTC grade 3 or 4 abnormalities was low (approximately 0.1%) in both treatment groups. Approximately 20% of patients receiving exemestane in clinical studies in advanced breast cancer experienced CTC grade 3 or 4 lymphocytopenia. Of these patients, 89% had a pre-existing lower grade lymphopenia. Forty percent of patients either recovered or improved to a lesser severity while on treatment. Patients did not have a significant increase in viral infections, and no opportunistic infections were observed. Elevations of serum levels of AST, ALT, alkaline phosphatase, and gamma glutamyl transferase >5 times the upper value of the normal range (i.e., ≥ CTC grade 3) have been rarely reported in patients treated for advanced breast cancer but appear mostly attributable to the underlying presence of liver and/or bone metastases. In the comparative study in advanced breast cancer patients, CTC grade 3 or 4 elevation of gamma glutamyl transferase without documented evidence of liver metastasis was reported in 2.7% of patients treated with exemestane tablets and in 1.8% of patients treated with megestrol acetate.

In patients with early breast cancer, elevations in bilirubin, alkaline phosphatase, and creatinine were more common in those receiving exemestane than either tamoxifen or placebo. Treatment-emergent bilirubin elevations (any CTC grade) occurred in 5% of exemestane patients and 0.8% of tamoxifen patients on the Intergroup Exemestane Study (IES), and in 7% of exemestane treated patients vs. 0% of placebo treated patients in the 027 study. CTC grade 3–4 increases in bilirubin occurred in 0.9% of exemestane treated patients compared to 0.1% of tamoxifen treated patients. Alkaline phosphatase elevations of any CTC grade occurred in 15% of exemestane treated patients on the IES compared to 2.6% of tamoxifen treated patients, and in 14% of exemestane treated patients compared to 7% of placebo treated patients in study 027. Creatinine elevations occurred in 6% of exemestane treated patients and 4.3% of tamoxifen treated patients on the IES and in 6% of exemestane treated patients and 0% of placebo treated patients in study 027.

5.5 Use in Premenopausal Women

Exemestane tablets are not indicated for the treatment of breast cancer in premenopausal women.

5.6 Embryo-Fetal Toxicity

Based on findings from animal studies and its mechanism of action, exemestane tablets can cause fetal harm when administered to a pregnant woman. In animal reproduction studies, administration of exemestane to pregnant rats and rabbits caused increased incidence of abortions and embryo-fetal toxicity. Advise pregnant women of the potential risk to a fetus. Advise females of reproductive potential to use effective contraception during treatment with exemestane tablets and for 1 month after the last dose [see Use in Specific Populations (8.1), (8.3) and Clinical Pharmacology (12.1)].

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DRUG INTERACTIONS SECTION

Highlight: Strong CYP 3A4 inducers: Concomitant use of strong CYP 3A4 inducers decreases exemestane exposure. Increase the exemestane tablets dose to 50 mg (2.2, 7).

7 DRUG INTERACTIONS

Drugs That Induce CYP 3A4

Co-medications that induce CYP 3A4 (e.g., rifampicin, phenytoin, carbamazepine, phenobarbital, or St. John's Wort) may significantly decrease exposure to exemestane. Dose modification is recommended for patients who are also receiving a strong CYP 3A4 inducer [see Dosage and Administration (2.2) and Clinical Pharmacology (12.3)].

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USE IN SPECIFIC POPULATIONS SECTION

Highlight: Lactation: Advise not to breastfeed (8.2).

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Risk Summary

Based on findings in animal studies and its mechanism of action, exemestane tablets can cause fetal harm when administered to a pregnant woman [see Clinical Pharmacology (12.1)]. Limited human data from case reports are insufficient to inform a drug-associated risk. In animal reproduction studies, administration of exemestane to pregnant rats and rabbits caused increased incidence of abortions, embryo-fetal toxicity, and prolonged gestation with abnormal or difficult labor [see Data]. Advise pregnant women of the potential risk to a fetus.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the US general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Data

Animal Data

In animal reproduction studies in rats and rabbits, exemestane caused embryo- fetal toxicity, and was abortifacient. Radioactivity related to 14C-exemestane crossed the placenta of rats following oral administration of 1 mg/kg exemestane. The concentration of exemestane and its metabolites was approximately equivalent in maternal and fetal blood. When rats were administered exemestane from 14 days prior to mating until either days 15 or 20 of gestation, and resuming for the 21 days of lactation, an increase in placental weight was seen at 4 mg/kg/day (approximately 1.5 times the recommended human daily dose on a mg/m2 basis). Increased resorptions, reduced number of live fetuses, decreased fetal weight, retarded ossification, prolonged gestation and abnormal or difficult labor was observed at doses equal to or greater than 20 mg/kg/day (approximately 7.5 times the recommended human daily dose on a mg/m2 basis). Daily doses of exemestane, given to rabbits during organogenesis, caused a decrease in placental weight at 90 mg/kg/day (approximately 70 times the recommended human daily dose on a mg/m2 basis) and in the presence of maternal toxicity, abortions, an increase in resorptions, and a reduction in fetal body weight were seen at 270 mg/kg/day. No malformations were noted when exemestane was administered to pregnant rats or rabbits during the organogenesis period at doses up to 810 and 270 mg/kg/day, respectively (approximately 320 and 210 times the recommended human dose on a mg/m2 basis, respectively).

8.2 Lactation

Risk Summary

There is no information on the presence of exemestane in human milk, or on its effects on the breastfed infant or milk production. Exemestane is present in rat milk at concentrations similar to maternal plasma [see Data]. Because of the potential for serious adverse reactions in breast-fed infants from exemestane tablets, advise a woman not to breastfeed during treatment with exemestane tablets and for 1 month after the final dose.

Data

Radioactivity related to exemestane appeared in rat milk within 15 minutes of oral administration of radiolabeled exemestane. Concentrations of exemestane and its metabolites were approximately equivalent in the milk and plasma of rats for 24 hours after a single oral dose of 1 mg/kg 14C-exemestane.

8.3 Females and Males of Reproductive Potential

Pregnancy Testing

Pregnancy testing is recommended for females of reproductive potential within seven days prior to initiating exemestane tablets.

Contraception

Females

Exemestane tablets can cause fetal harm when administered to a pregnant woman [see Use in Specific Populations (8.1)]. Advise females of reproductive potential to use effective contraception during treatment with exemestane tablets and for 1 month after the final dose.

Infertility

Based on findings in animals, male and female fertility may be impaired by treatment with exemestane tablets [see Nonclinical Toxicology (13.1)].

8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

8.6 Hepatic Impairment

The AUC of exemestane was increased in subjects with moderate or severe hepatic impairment (Childs-Pugh B or C) [see Clinical Pharmacology (12.3)]. However, based on experience with exemestane at repeated doses up to 200 mg daily that demonstrated a moderate increase in non life-threatening adverse reactions, dosage adjustment does not appear to be necessary.

8.7 Renal Impairment

The AUC of exemestane was increased in subjects with moderate or severe renal impairment (creatinine clearance <35 mL/min/1.73 m2) [see Clinical Pharmacology (12.3)]. However, based on experience with exemestane at repeated doses up to 200 mg daily that demonstrated a moderate increase in non life- threatening adverse reactions, dosage adjustment does not appear to be necessary.

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CLINICAL STUDIES SECTION

14 CLINICAL STUDIES

14.1 Adjuvant Treatment in Early Breast Cancer

The Intergroup Exemestane Study 031 (IES) was a randomized, double-blind, multicenter, multinational study comparing exemestane (25 mg/day) vs. tamoxifen (20 or 30 mg/day) in postmenopausal women with early breast cancer. Patients who remained disease-free after receiving adjuvant tamoxifen therapy for 2 to 3 years were randomized to receive an additional 3 or 2 years of exemestane tablets or tamoxifen to complete a total of 5 years of hormonal therapy.

The primary objective of the study was to determine whether, in terms of disease-free survival, it was more effective to switch to exemestane tablets rather than continuing tamoxifen therapy for the remainder of five years. Disease- free survival was defined as the time from randomization to time of local or distant recurrence of breast cancer, contralateral invasive breast cancer, or death from any cause.

The secondary objectives were to compare the two regimens in terms of overall survival and long-term tolerability. Time to contralateral invasive breast cancer and distant recurrence-free survival were also evaluated.

A total of 4724 patients in the intent-to-treat (ITT) analysis were randomized to exemestane tablets 25 mg once daily (N = 2352) or to continue to receive tamoxifen once daily at the same dose received before randomization (N = 2372). Demographics and baseline tumor characteristics are presented in Table 5. Prior breast cancer therapy is summarized in Table 6.

Table 5. Demographic and Baseline Tumor Characteristics from the IES Study of Postmenopausal Women with Early Breast Cancer (ITT Population) Table 6. Prior Breast Cancer Therapy of Patients in the IES Study of Postmenopausal Women with Early Breast Cancer (ITT Population)

After a median duration of therapy of 27 months and with a median follow-up of 34.5 months, 520 events were reported, 213 in the exemestane tablets group and 307 in the tamoxifen group (Table 7).

Table 7. Primary Endpoint Events (ITT Population)

Disease-free survival in the intent-to-treat population was statistically significantly improved [Hazard Ratio (HR) = 0.69, 95% CI: 0.58, 0.82, P = 0.00003, Table 8, Figure 1] in the exemestane tablets arm compared to the tamoxifen arm. In the hormone receptor-positive subpopulation representing about 85% of the trial patients, disease-free survival was also statistically significantly improved (HR = 0.65, 95% CI: 0.53, 0.79, P = 0.00001) in the exemestane tablets arm compared to the tamoxifen arm. Consistent results were observed in the subgroups of patients with node negative or positive disease, and patients who had or had not received prior chemotherapy.

An overall survival update at 119 months median follow-up showed no significant difference between the two groups, with 467 deaths (19.9%) occurring in the exemestane tablets group and 510 deaths (21.5%) in the tamoxifen group.

Table 8. Efficacy Results from the IES Study in Postmenopausal Women with Early Breast Cancer

Figure 1. Disease-Free Survival in the IES Study of Postmenopausal Women with Early Breast Cancer (ITT Population)

14.2 Treatment of Advanced Breast Cancer

Exemestane 25 mg administered once daily was evaluated in a randomized double- blind, multicenter, multinational comparative study and in two multicenter single-arm studies of postmenopausal women with advanced breast cancer who had disease progression after treatment with tamoxifen for metastatic disease or as adjuvant therapy. Some patients also have received prior cytotoxic therapy, either as adjuvant treatment or for metastatic disease.

The primary purpose of the three studies was evaluation of objective response rate (complete response [CR] and partial response [PR]). Time to tumor progression and overall survival were also assessed in the comparative trial. Response rates were assessed based on World Health Organization (WHO) criteria, and in the comparative study, were submitted to an external review committee that was blinded to patient treatment. In the comparative study, 769 patients were randomized to receive exemestane tablets 25 mg once daily (N = 366) or megestrol acetate 40 mg four times daily (N = 403). Demographics and baseline characteristics are presented in Table 9.

Table 9. Demographics and Baseline Characteristics from the Comparative Study of Postmenopausal Women with Advanced Breast Cancer Whose Disease Had Progressed after Tamoxifen Therapy

The efficacy results from the comparative study are shown in Table 10. The objective response rates observed in the two treatment arms showed that exemestane tablets was not different from megestrol acetate. Response rates for exemestane tablets from the two single-arm trials were 23.4% and 28.1%.

Table 10. Efficacy Results from the Comparative Study of Postmenopausal Women with Advanced Breast Cancer Whose Disease Had Progressed after Tamoxifen Therapy

There were too few deaths occurring across treatment groups to draw conclusions on overall survival differences. The Kaplan-Meier curve for time to tumor progression in the comparative study is shown in Figure 2.

Figure 2. Time to Tumor Progression in the Comparative Study of Postmenopausal Women With Advanced Breast Cancer Whose Disease Had Progressed After Tamoxifen Therapy

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OVERDOSAGE SECTION

10 OVERDOSAGE

Clinical trials have been conducted with exemestane given as a single dose to healthy female volunteers at doses as high as 800 mg and daily for 12 weeks to postmenopausal women with advanced breast cancer at doses as high as 600 mg. These dosages were well tolerated. There is no specific antidote to overdosage and treatment must be symptomatic. General supportive care, including frequent monitoring of vital signs and close observation of the patient, is indicated.

A male child (age unknown) accidentally ingested a 25-mg tablet of exemestane. The initial physical examination was normal, but blood tests performed 1 hour after ingestion indicated leucocytosis (WBC 25000/mm3 with 90% neutrophils). Blood tests were repeated 4 days after the incident and were normal. No treatment was given.

In mice, mortality was observed after a single oral dose of exemestane of 3200 mg/kg, the lowest dose tested (about 640 times the recommended human dose on a mg/m2 basis). In rats and dogs, mortality was observed after single oral doses of exemestane of 5000 mg/kg (about 2000 times the recommended human dose on a mg/m2 basis) and of 3000 mg/kg (about 4000 times the recommended human dose on a mg/m2 basis), respectively.

Convulsions were observed after single doses of exemestane of 400 mg/kg and 3000 mg/kg in mice and dogs (approximately 80 and 4000 times the recommended human dose on a mg/m2 basis), respectively.

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NONCLINICAL TOXICOLOGY SECTION

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

A 2-year carcinogenicity study in mice at doses of 50, 150, and 450 mg/kg/day exemestane (gavage), resulted in an increased incidence of hepatocellular adenomas and/or carcinomas in both genders at the high dose level. Plasma AUC (0–24hr) at the high dose were 2575 ± 386 and 5667 ± 1833 ng.hr/mL in males and females (approx. 34 and 75 fold the AUC in postmenopausal patients at the recommended clinical dose). An increased incidence of renal tubular adenomas was observed in male mice at the high dose of 450 mg/kg/day. Since the doses tested in mice did not achieve an MTD, neoplastic findings in organs other than liver and kidneys remain unknown.

A separate carcinogenicity study was conducted in rats at the doses of 30, 100, and 315 mg/kg/day exemestane (gavage) for 92 weeks in males and 2 years in females. No evidence of carcinogenic activity up to the highest dose tested of 315 mg/kg/day was observed in females. The male rat study was inconclusive since it was terminated prematurely at Week 92. At the highest dose, plasma AUC(0–24hr) levels in male (1418 ± 287 ng.hr/mL) and female (2318 ± 1067 ng.hr/mL) rats were 19 and 31 fold higher than those measured in postmenopausal cancer patients receiving the recommended clinical dose.

Exemestane was not mutagenic in vitro in bacteria (Ames test) or mammalian cells (V79 Chinese hamster lung cells). Exemestane was clastogenic in human lymphocytes in vitro without metabolic activation but was not clastogenic in vivo (micronucleus assay in mouse bone marrow). Exemestane did not increase unscheduled DNA synthesis in rat hepatocytes when tested in vitro.

In a pilot reproductive study in rats, male rats were treated with doses of 125–1000 mg/kg/day exemestane, beginning 63 days prior to and during cohabitation. Untreated female rats showed reduced fertility when mated to males treated with ≥500 mg/kg/day exemestane (≥200 times the recommended human dose on a mg/m2 basis). In a separate study, exemestane was given to female rats at 4–100 mg/kg/day beginning 14 days prior to mating and through day 15 or 20 of gestation. Exemestane increased the placental weights at ≥4 mg/kg/day (≥1.5 times the human dose on a mg/m2 basis). Exemestane showed no effects on ovarian function, mating behavior, and conception rate in rats given doses up to 20 mg/kg/day (approximately 8 times the recommended human dose on a mg/m2 basis); however, decreases in mean litter size and fetal body weight, along with delayed ossification were evidenced at ≥20 mg/kg/day. In general toxicology studies, changes in the ovary, including hyperplasia, an increase in the incidence of ovarian cysts, and a decrease in corpora lutea were observed with variable frequency in mice, rats, and dogs at doses that ranged from 3–20 times the human dose on a mg/m2 basis**.**

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INFORMATION FOR PATIENTS SECTION

17 PATIENT COUNSELING INFORMATION

Advise the patient to read the FDA-approved patient labeling (Patient Information).

Bone Effects

Advise patients that exemestane tablets lower the level of estrogen in the body. This may lead to reduction in bone mineral density (BMD) over time. The lower the BMD, the greater the risk of osteoporosis and fracture [see Warnings and Precautions (5.1)].

Other Estrogen-Containing Agents

Advise patients that they should not take estrogen-containing agents while they are taking exemestane tablets as these could interfere with its pharmacologic action [see Warnings and Precautions (5.3)].

Use in Premenopausal Women

Advise patients that exemestane tablets are not for use for the treatment of breast cancer in premenopausal women [see Warnings and Precautions (5.5)].

Embryo-Fetal Toxicity

Advise pregnant women and females of reproductive potential that exposure during pregnancy or within 1 month prior to conception can result in fetal harm. Advise females to inform their healthcare provider of a known or suspected pregnancy [see Warnings and Precautions (5.6) and Use in Specific Populations (8.1)].

Advise females of reproductive potential to use effective contraception while taking exemestane tablets and for 1 month after the last dose [see Use in Specific Populations (8.3)].

Lactation

Advise women not to breastfeed during treatment with exemestane tablets and for 1 month after the last dose [see Use in Specific Populations (8.2)].

SPL PATIENT PACKAGE INSERT SECTION

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SPL UNCLASSIFIED SECTION

Manufactured by:
MSN Laboratories Private Limited
Telangana – 509 228,
INDIA

Distributed by:
Breckenridge Pharmaceutical, Inc.
Berkeley Heights, NJ 07922

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