Proprietary name: APO-Exemestane tablets Non proprietary name: Exemestane tablets Chemical name: 6-methylenandrosta-1,4-diene-3,17-dione. The chemical structure of exemestane is: CAS number: 107868-30-4

DESCRIPTION

Exemestane is a white or yellowish white powder, which is freely soluble in N,N- dimethylformamide, soluble in methanol and practically insoluble in water. Due to the very low solubility in water, the drug is micronised. Molecular formula: C20H24O2 Molecular Weight: 296.4

Excipients

Microcrystalline cellulose, crospovidone, polysorbate 80, mannitol, anhydrous colloidal silica, magnesium stearate, sucrose, acacia, purified talc, titanium dioxide, shellac, beeswax white, and carnauba wax yellow.

PHARMACOLOGY

Pharmacodynamics

Exemestane is an irreversible, steroidal aromatase inactivator, structurally related to the natural substrate androstenedione. In postmenopausal women, oestrogens are produced primarily from the conversion of androgens into oestrogens through the aromatase enzyme in peripheral tissues. Oestrogen deprivation through aromatase inhibition is an effective and selective treatment for hormone dependent breast cancer in postmenopausal women. Exemestane acts by binding irreversibly to the active site of the enzyme causing its inactivation. Such a type of inactivation is also known as "suicidal inhibition". In postmenopausal women, exemestane significantly lowered serum oestrogen concentrations starting from a 5 mg dose, reaching maximal suppression (80 to 90%) with a dose of 10 to 25 mg. In postmenopausal breast cancer patients treated with the 25 mg daily dose, whole body aromatisation was reduced by 98%. Exemestane does not possess any progestogenic or oestrogenic activity. A slight androgenic activity, probably due to the 17-hydro derivative, has been observed mainly, at high doses. In trials with multiple daily doses, exemestane had no detectable effects on adrenal biosynthesis of cortisol or aldosterone, measured before or after adrenocorticotrophic hormone (ACTH) challenge, thus demonstrating its selectivity with regard to the other enzymes involved in the steroidogenic pathway. Glucocorticoid or mineralocorticoid replacements are therefore not needed. A nondose dependent slight increase in serum luteinising hormone (LH) and follicle stimulating hormone (FSH) levels has been observed even at low doses. This effect is expected for the pharmacological class and is probably the result of feedback at the pituitary level due to reduction in oestrogen levels stimulating pituitary secretion of gonadotrophins. A dose related decrease in sex hormone binding globulin (SHBG) was observed, which occurred with exemestane 25 mg/day. A substudy of endometrial thickness was done in the early breast cancer trial 031 in patients who had received two to three years of tamoxifen treatment. The substudy contained 113 patients, 61 of whom received exemestane and 52 continued on tamoxifen. At baseline, 64% of exemestane patients and 63% of tamoxifen patients had abnormal endometrial thickening (>= 5 mm on ultrasound). After two years, the proportion of exemestane patients with abnormal endometrial thickening had decreased to 36% whereas the proportion of tamoxifen patients with abnormal endometrial thickening remained near baseline at 64%. The difference between treatments after adjusting for baseline was statistically significant (p = 0.0025).

Pharmacokinetics

Following oral administration, exemestane is rapidly and extensively absorbed, although animal data suggest that the absolute bioavailability is low due to an extensive first-pass effect. At a single dose of 25 mg given after a meal, average peak plasma levels of 18 nanogram/mL are achieved within two hours postdosing. Food was shown to enhance absorption, resulting in plasma levels 30 to 40% higher than those observed in subjects under fasting conditions.

After the peak, plasma levels of exemestane decline in a polyexponential manner with a terminal half-life of approximately 24 hours. The plasma protein binding of exemestane is approximately 90% and the fraction bound is independent of total concentration. The distribution of the drug and/or its metabolites into blood cells is negligible.

No significant deviations from dose proportional pharmacokinetics were observed in healthy volunteers up to a 50 mg oral dose. Following repeated daily administration of 25 mg, plasma concentrations of the unchanged drug were of a similar order to those measured after single dosing. Following oral administration of a single dose of radiolabelled exemestane, the elimination of drug related products was shown to be essentially complete within one week, with approximately equal proportions of the dose eliminated in urine and faeces. The amount of drug excreted unchanged in urine is less than 1% of the dose. The biotransformation proceeds through oxidation of the methylene group at position 6 via the CYP3A4 isoenzyme and/or reduction of 17-keto group by aldoketoreductases. Subsequently, many secondary metabolites are formed, each accounting for a limited amount of the dose. The metabolites are either inactive or less active than the parent drug in inhibiting aromatase.

Special populations

No significant correlation between the systemic exposure of exemestane and the age of subjects has been observed.

Exemestane pharmacokinetics have been investigated in subjects with severe renal insufficiency (CLCR <= 30 mL/minute). In these subjects the systemic exposure to exemestane after a single dose was found to be approximately double that of healthy volunteers. This difference, although pharmacokinetically significant, is unlikely to require dose adjustment, given the good tolerability observed in humans at doses up to eight times the recommended dose. However, exemestane should be used with caution in patients with renal insufficiency.

Exemestane pharmacokinetics have been investigated in subjects with moderate and severe hepatic insufficiency. The systemic exposure to exemestane was two to three times higher than in healthy volunteers. As for renal insufficiency, dose adjustment is unlikely to be required. However, exemestane should be used with caution in patients with hepatic impairment.

CLINICAL TRIALS

Sequential adjuvant treatment of early breast cancer

In a multicentre, randomised, double blind study (number 031), conducted in 4,724 postmenopausal patients with oestrogen receptor positive or unknown primary breast cancer, patients who had remained disease free after receiving adjuvant tamoxifen therapy for two to three years were randomised to receive three to two years of exemestane (25 mg/day) or tamoxifen (20 or 30 mg/day) to complete a total of five years of hormonal therapy.

Exemestane Table 1

Efficacy results from study 031 in postmenopausal women with early breast cancer (ITT)

Exemestane Figure 1

Disease Free Survival in Study 031 of Postmenopausal Women with Early Breast Cancer After a median duration of therapy of about 30 months and a median follow-up of about 52 months, sequential treatment with exemestane after two to three years of adjuvant tamoxifen therapy significantly increased disease free survival (DFS), compared with continuation of tamoxifen (see Table 1 and Figure 1). Exemestane also significantly increased breast cancer free survival and reduced the risk of contralateral breast cancer and distant recurrence (see Table 1). A trend for improved overall survival was observed for exemestane (222 deaths) compared to tamoxifen (262 deaths) with a hazard ratio of 0.85 (log rank test: p = 0.07362), representing a 15% reduction in the risk of death in favour of exemestane.

Treatment of advanced breast cancer

Efficacy data in patients progressing while on antioestrogen therapy (second line treatment) include results from a phase III study (multicentre, multinational, peer reviewed, randomised, double blind, controlled) with exemestane 25 mg daily versus megestrol acetate 40 mg qid (four times daily) in 763 patients. All patients had failed on prior tamoxifen treatment. The population characteristics were representative of postmenopausal patients with relapsed advanced breast cancer. The median age was 65 years. Various races were represented, the majority being caucasian. Most patients (70%) were oestrogen receptor/ progesterone receptor positive and most had measurable disease. Almost 50% had predominantly visceral disease. The peer reviewed results of this controlled study indicate that exemestane and megestrol acetate are equivalent in terms of objective responses, with objective response rates of 12.4% for megestrol acetate versus 15.0% for exemestane (confidence interval (CI) for difference: -7.5; +2.3). Overall success rates (complete response, partial response or no change) are also comparable, 37.4% for exemestane versus 34.6% for megestrol acetate. Conversely, duration of overall success (median: 60.1 versus 49.1 weeks, p = 0.025), time to progression (median: 20.3 versus 16.6 weeks, p = 0.037), time to treatment failure (median: 16.3 versus 15.7 weeks, p = 0.042), and survival (median not yet achieved versus 123.4 weeks, p = 0.039) are significantly longer in exemestane treated patients than in those treated with megestrol acetate. The point estimates for survival at the 25th percentile (75% survival) are 74.6 weeks (95% CI 59.1 to 91.0) for exemestane and 55.0 weeks (95% CI 46.1 to 70.3) for megestrol acetate. The Kaplan Meier curve for time to tumour progression is shown in Figure 2.

Exemestane Figure 2

Probability Time to tumour progression in the comparative study of exemestane and megestrol acetate Weeks Efficacy was also observed in patients having progressed following multiple hormone therapies (third line therapy). Three peer reviewed uncontrolled phase II studies were conducted at the recommended dose of exemestane 25 mg. In the combined analysis, which was of the descriptive type, exemestane induced objective response, with a median duration of 61 weeks, in 9% of the patients (95% CI 6 to 12) and overall clinical benefit, with a median duration of 37 weeks, in 26% of the cases (95% CI 22 to 31). Although survival cannot yet be estimated in each of the three studies, median survival in the overall population (intent to treat) was approximately 30 months (131.1 weeks, 95% CI 100.0 to 147.1 weeks). Exemestane was effective both in patients experiencing failure of megestrol acetate and failure of other nonsteroidal aromatase inhibitors.

CONTRAINDICATIONS

Pregnant or lactating women and patients with a known hypersensitivity to the drug or to any of the excipients

PRECAUTIONS

Check the following before use

Because of its mode of action, exemestane should not be administered to women with pre- menopausal endocrine status. Whenever clinically appropriate, confirmation of post- menopausal status may be assisted by laboratory tests, such as assessment of luteinising (LH), follicle stimulating hormone (FSH) and oestradiol levels.

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

Bone mineral density

Reductions in bone mineral density over time are seen with exemestane use. In a sub-study of trial 031 in early breast cancer, patients who received two years of exemestane after two to three years of tamoxifen (n = 86) had a higher loss of bone mineral density in the spine, hip, femoral neck and Ward's triangle than patients who received continuous tamoxifen (n = 100) (mean loss varied from two percentage points greater at the hip to five percentage points greater in Ward's triangle). Overall, in trial 031, the incidence of fracture was greater in patients treated with exemestane than tamoxifen (see Adverse Reactions). The impact of exemestane on long-term fracture risk remains to be determined. As exemestane is a potent oestrogen lowering agent, reduction in bone mineral density can be anticipated. During adjuvant treatment with exemestane, women with osteoporosis or at risk of developing osteoporosis should have their bone mineral density formally assessed by bone densitometry at the commencement of treatment and at regular intervals thereafter. Treatment or prophylaxis for osteoporosis should be initiated as appropriate and carefully monitored.

Effects on fertility

Untreated female rats showed reduced fertility when mated to males treated with exemestane 500 mg/kg/day (approximately 200 times the recommended human dose on a mg/m2 basis). Exemestane given to female rats showed no effects on female fertility parameters (e.g. ovarian function, mating behaviour, conception rate) at doses up to 20 mg/kg/day (approximately eight times the human dose on a mg/m2 basis), but mean litter size was decreased at this dose. In general toxicology studies, changes in the ovary, including atrophy, tubulostromal hyperplasia, an increase in ovarian cysts and a decrease in corpora lutea were observed with variable frequency in mice, rats and/or dogs at doses that ranged from 3 to 20 times the human dose on a mg/m2 basis.

Use in pregnancy (Category "C")

Category "C": Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible. Accompanying texts should be consulted for further details.

Exemestane disrupts oestrogen dependent metabolism and may result in abortion. It is contraindicated in pregnant women. In rats the concentration of exemestane and its metabolites was approximately equivalent in maternal and fetal blood. When rats were administered exemestane until either days 15 or 20 of gestation, 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). Prolonged gestation and abnormal or difficult labour were observed at doses equal to or greater than 20 mg/kg/day. Increased resorption, reduced number of live fetuses, decreased fetal weight and retarded ossification were also observed at these doses. No malformations were noted when exemestane was administered to pregnant rats during the organogenesis period at doses up to 810 mg/kg/day (approximately 320 times the recommended human 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). Abortions, an increase in resorptions and a reduction in fetal bodyweight were seen at 270 mg/kg/day (approximately 210 times the recommended human dose on a mg/m2 basis). There was no increase in the incidence of malformations in rabbits at doses up to 270 mg/kg/day. There are no studies in pregnant women using exemestane. Exemestane is indicated for postmenopausal women. If there is exposure to exemestane during pregnancy, the patient should be advised of the potential hazard to the fetus and potential risk for loss of the pregnancy.

Use in lactation

Exemestane is contraindicated in pregnant women and only indicated in postmenopausal women. Exemestane and/or its metabolites appeared in rat milk within 15 minutes of oral administration of radiolabelled 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. It is not known whether exemestane is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised if a breastfeeding woman is inadvertently exposed to exemestane.

Genotoxicity

Exemestane was not mutagenic in bacteria (Ames test), in V79 Chinese hamster cells nor did it cause DNA damage in rat hepatocytes. Although exemestane was clastogenic in lymphocytes in vitro, it was not clastogenic in two in vivo studies.

Carcinogenicity

A two year carcinogenicity study in mice at doses of exemestane 50, 150 and 450 mg/kg/day (gavage) resulted in an increased incidence of hepatocellular adenomas and/or carcinomas at doses > 50 mg/kg/day in males and > 150 mg/kg/day in females. Exposures (plasma AUC) at these doses were 4 and 37 times, respectively, exposure in patients at the recommended dose. However, statistical significance was only reached at the high dose exposures (approximately 34 (male) and 75 (female) fold the AUC in patients). An increased incidence of renal tubular adenomas was observed in male mice at the high dose of 450 mg/kg/day. A carcinogenicity study was conducted in rats at doses of 30, 100 and 315 mg/kg/day (gavage) for 92 weeks in males and two years in females. No evidence of carcinogenic activity up to the highest dose tested (315 mg/kg/day) was observed. At the highest dose, plasma AUC (0 to 24 hour) levels in male and female rats were 19 and 31-fold higher than those measured in the postmenopausal cancer patients receiving the recommended clinical dose.

Effect on ability to drive or operate machinery

Exemestane is unlikely to impair the ability of patients to drive and operate machinery. However, drowsiness, somnolence, asthenia and dizziness have been reported with the use of the drug. Patients should be advised that, if these events occur, their physical and/or mental abilities required for operating machinery or driving a car may be impaired.

Effects on laboratory tests

Elevation of serum hepatic function tests (especially ALT and GGT) and alkaline phosphatase have been occasionally observed. In the pivotal controlled study these elevations occurred mainly in patients with liver or bone metastases or other impaired liver conditions, except for the elevations in GGT. Decreases in WBC, especially lymphocytes, were also observed

INTERACTIONS WITH OTHER MEDICINES

Exemestane should not be coadministered with oestrogen containing products as these would negate its pharmacological action. No formal drug interaction studies have been carried out. In vitro evidence showed that the drug is metabolised through cytochrome P450 (CYP) 3A4 and aldoketoreductases and does not inhibit any of the major CYP isoenzymes. In a clinical pharmacokinetic study, the specific inhibition of CYP3A4 by ketoconazole showed no significant effects on the pharmacokinetics of exemestane. A possible decrease of exemestane plasma levels by known inducers of CYP3A4 cannot be excluded. Exemestane should be used cautiously with drugs that are metabolised via CYP3A4 and have a narrow therapeutic window.

ADVERSE EFFECTS

Exemestane was generally well tolerated across all clinical studies; adverse events were usually mild to moderate. The discontinuation rate due to adverse events was 7.4% in patients with early breast cancer receiving adjuvant treatment with exemestane following initial adjuvant tamoxifen therapy. The most commonly reported adverse reactions were hot flushes (22%), arthralgia (18%) and fatigue (16%). The discontinuation rate due to adverse events was 2.8% in the overall patient population with advanced breast cancer. The most commonly reported adverse reactions were hot flushes (14%) and nausea (12%). Most adverse reactions can be attributed to the normal pharmacological consequences of oestrogen deprivation (e.g. hot flushes). Adverse events in which causal relationship with exemestane could not be excluded are listed below by system organ class and by frequency. Frequencies are defined as follows. Very common (> 10%), common (> 1%, <= 10%), uncommon (> 0.1%, <= 1%), rare (> 0.01%, <= 0.1%).

Body as a whole

Very common:hot flushes, fatigue. Common:pain, peripheral or leg oedema.

Gastrointestinal disorders

Very common:nausea, serum alkaline phosphatase increase. Common:abdominal pain, anorexia, vomiting, constipation, dyspepsia, diarrhoea, bilirubin increase, ALT increase. Uncommon:GGT increase#.

Autonomic nervous system

Very common:increased sweating.

Central and peripheral nervous system

Very common:headache.

Common:dizziness, carpal tunnel syndrome. Psychiatric disorders Very common:insomnia. Common:depression.

Skin and appendages

Common:rash, alopecia.

Musculoskeletal and bone disorders

Very common:joint and musculoskeletal pain (includes arthralgia and less frequently pain in limb, osteoarthritis, back pain, arthritis, myalgia and joint stiffness). Common:osteoporosis, fracture.

Haematological

Very common:lymphocyte decrease#. Uncommon:leucopenia#, thrombocytopenia#. # Events observed in patients with advanced breast cancer. Treatment emergent adverse events and illnesses including all causalities and occurring with an incidence of >= 5% in either treatment group in study 031 during or within one month of the end of the study are shown in Table 2.

Exemestane Table 2

Adverse events1 and illnesses with incidence >=5% and/or a significant difference ++ between exemestane and tamoxifen in study 031 in early breast cancer (median follow-up about 52 months)

Body system and adverse events by MedDRA dictionary	% of patients
Body system and adverse events by MedDRA dictionary	Exemestane 25 mg daily (N=2249)	Tamoxifen 20 mg daily 2 (N=2279)
Cardiovascular ++ Hypertension Thromboembolism Gastrointestinal Nausea 3 Diarrhoea ++ Gastric ulcer ++ General disorders 3 Hot flushes Fatigue Gynaecological Vaginal haemorrhage Endometrial hyperplasia ++ Uterine polyp ++ Uterine polypectomy Investigations Weight increased Metabolism and nutrition Hypercholesterolaemia ++ Musculoskeletal Arthralgia ++ Back pain Pain in limb Osteoarthritis ++ Osteoporosis Muscle cramp ++ Nervous Headache 3 Dizziness 3 Paraesthesia ++ Carpal tunnel syndrome ++ Neuropathy ++ Psychiatric Insomnia ++ Depression Skin & subcutaneous tissue Increased sweating 3	9.9 0.7 8.9 4.2 0.7 21.8 16.3 4.0 <0.1 0.4 0.2 5.7 3.7 17.6 9.3 6.4 6.1 5.2 1.4 13.6 10.0 2.8 2.8 0.5 12.9 6.2 12.0	8.4 1.8 9.1 2.2 <0.1 20.1 15.1 5.3 0.9 1.8 0.8 6.1 2.1 10.8 7.7 4.7 4.7 2.9 3.2 11.2 8.8 1.0 0.2 <0.1 9.0 5.6 10.6

++ Indicates a significant difference at 1% level. 1 Graded according to Common Toxicicty Criteria. 2 75 patients received tamoxifen 30 mg daily. 3 Event actively sought. The incidence of myocardial infarction (0.6 versus 0.2%, p = 0.030) and cardiac failure (1.1 versus 0.7%, p = 0.123) in patients treated with exemestane compared with those treated with tamoxifen was not significant at the nominal significance level of 0.01 used to allow for multiple testing. Treatment-emergent fractures were more frequent in exemestane patients (4.5%) than in tamoxifen patients (3.3%). When fractures reported on treatment and during follow-up are considered, the incidence was significantly greater in exemestane patients (7.0%) compared with tamoxifen patients (4.9%), p = 0.002.

Post-marketing Experience

Immune system disorders *

Hypersensitivity *

Hepatobiliary disorders *

Rare cases of hepatitis including cholestatic hepatitis have been observed in clinical trials and reported through post-marketing surveillance.

Skin and subcutaneous tissue disorders *

Urticaria *, pruritus *

DOSAGE AND ADMINISTRATION

Adults

The recommended dose of exemestane in adults is one 25 mg tablet taken once daily, preferably after a meal. In patients with early breast cancer, treatment should continue until completion of five years adjuvant hormonal therapy or until tumour relapse occurs. In patients with advanced breast cancer, treatment with exemestane should continue until tumour progression is evident. No dose adjustments are required for patients with hepatic or renal insufficiency.

Children

OVERDOSAGE

Clinical trials have been conducted with exemestane given up to 800 mg in a single dose to healthy female volunteers and up to 600 mg daily to postmenopausal women with advanced breast cancer. These dosages were well tolerated. The single dose of exemestane that could result in life threatening symptoms is not known. There is no specific antidote to overdosage and treatment should be symptomatic. General supportive care, including frequent monitoring of vital signs and close observation of the patient, is indicated. Consider administration of activated charcoal in the event of a potentially toxic ingestion. Activated charcoal is most effective when administered within one hour of ingestion. In patients who are not fully conscious or have impaired gag reflex, consideration should be given to administering activated charcoal via nasogastric tube once the airway is protected. Haemodialysis is not expected to significantly enhance the clearance of exemestane due to extensive protein binding. Contact the Poisons Information Centre on 131 126 for advice on the management of an overdose.

PRESENTATION AND STORAGE CONDITIONS

APO-Exemestane 25 mg tablets are white to off-white, circular, biconvex and are sugar- coated: 30's blister pack. AUST R number:177312.

	KM probability *, %		Hazard Ratio
	Exemestane (N=2352)	Tamoxifen (N=2372)	Hazard Ratio (95% Cl)	p-value * *
Disease free	90.9	87.5	0.76 (0.67-0.88)	0.00015
survival	92.6	89.2	0.76 (0.65-0.89)	0.00041
Breast cancer free
survival	99.6	99.0	0.57 (0.33-0.99)	0.04158
Time to
contralateral breast	93.8	91.2	0.83 (0.70-0.98)	0.02621
cancer
Distant recurrence	95.3	94.2	0.85 (0.71-1.02)	0.07362
free survival
Overall survival

APO-Exemestane

NAME OF THE MEDICINE