Arimidex Information
Arimidex (Anastrozole) Dosage And Administration
The dose of Arimidex (Anastrozole) is one 1 mg tablet taken once a day. For patients with advanced breast cancer, Arimidex (Anastrozole) should be continued until tumor progression. Arimidex (Anastrozole) can be taken with or without food.
For adjuvant treatment of early breast cancer in postmenopausal women, the optimal duration of therapy is unknown. In the ATAC trial, Arimidex (Anastrozole) was administered for five years [see ].
No dosage adjustment is necessary for patients with renal impairment or for elderly patients [see ].
Arimidex (Anastrozole) Dosage Forms And Strengths
The tablets are white, biconvex, film-coated containing 1 mg of anastrozole. The tablets are impressed on one side with a logo consisting of a letter “A” (upper case) with an arrowhead attached to the foot of the extended right leg of the “A” and on the reverse with the tablet strength marking “Adx 1”.
Arimidex (Anastrozole) Adverse Reactions
Serious adverse reactions with Arimidex (Anastrozole) occurring in less than 1 in 10,000 patients, are: 1) skin reactions such as lesions, ulcers, or blisters; 2) allergic reactions with swelling of the face, lips, tongue, and/or throat. This may cause difficulty in swallowing and/or breathing; and 3) changes in blood tests of the liver function, including inflammation of the liver with symptoms that may include a general feeling of not being well, with or without jaundice, liver pain or liver swelling [see ].
Common adverse reactions (occurring with an incidence of >10%) in women taking Arimidex (Anastrozole) included: hot flashes, asthenia, arthritis, pain, arthralgia, pharyngitis, hypertension, depression, nausea and vomiting, rash, osteoporosis, fractures, back pain, insomnia, pain, headache, bone pain, peripheral edema, increased cough, dyspnea, pharyngitis and lymphedema.
In the ATAC trial, the most common reported adverse reaction (>0.1%) leading to discontinuation of therapy for both treatment groups was hot flashes, although there were fewer patients who discontinued therapy as a result of hot flashes in the Arimidex (Anastrozole) group.
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
Arimidex (Anastrozole) Use In Specific Populations
PREGNANCY CATEGORY X [see )]
Arimidex (Anastrozole) may cause fetal harm when administered to a pregnant woman and offers no clinical benefit to premenopausal women with breast cancer. Arimidex (Anastrozole) is contraindicated in women who are or may become pregnant. In animal studies, anastrozole caused pregnancy failure, increased pregnancy loss, and signs of delayed fetal development. There are no studies of Arimidex (Anastrozole) use in pregnant women. If Arimidex (Anastrozole) is used during pregnancy, or if the patient becomes pregnant while receiving this drug, the patient should be apprised of the potential hazard to the fetus and potential risk for pregnancy loss.
In animal reproduction studies, pregnant rats and rabbits received anastrozole during organogenesis at doses equal to or greater than 1 (rats) and 1/3 (rabbits) the recommended human dose on a mg/m basis. In both species, anastrozole crossed the placenta, and there was increased pregnancy loss (increased pre- and/or post-implantation loss, increased resorption, and decreased numbers of live fetuses). In rats, these effects were dose related, and placental weights were significantly increased. Fetotoxicity, including delayed fetal development (i.e., incomplete ossification and depressed fetal body weights), occurred in rats at anastrozole doses that produced peak plasma levels 19 times higher than serum levels in humans at the therapeutic dose (AUC 9 times higher). In rabbits, anastrozole caused pregnancy failure at doses equal to or greater than 16 times the recommended human dose on a mg/mbasis [see ].
Clinical studies in pediatric patients included a placebo-controlled trial in pubertal boys of adolescent age with gynecomastia and a single-arm trial in girls with McCune-Albright Syndrome and progressive precocious puberty. The efficacy of Arimidex (Anastrozole) in the treatment of pubertal gynecomastia in adolescent boys and in the treatment of precocious puberty in girls with McCune-Albright Syndrome has not been demonstrated.
Gynecomastia Study
A randomized, double-blind, placebo-controlled, multi-center study enrolled 80 boys with pubertal gynecomastia aged 11 to 18 years. Patients were randomized to a daily regimen of either Arimidex (Anastrozole) 1 mg or placebo. After 6 months of treatment there was no statistically significant difference in the percentage of patients who experienced a ≥50% reduction in gynecomastia (primary efficacy analysis). Secondary efficacy analyses (absolute change in breast volume, the percentage of patients who had any reduction in the calculated volume of gynecomastia, breast pain resolution) were consistent with the primary efficacy analysis. Serum estradiol concentrations at Month 6 of treatment were reduced by 15.4% in the Arimidex (Anastrozole) group and 4.5% in the placebo group.
Adverse reactions that were assessed as treatment-related by the investigators occurred in 16.3% of the Arimidex (Anastrozole) -treated patients and 8.1% of the placebo-treated patients with the most frequent being acne (7% Arimidex (Anastrozole) and 2.7% placebo) and headache (7% Arimidex (Anastrozole) and 0% placebo); all other adverse reactions showed small differences between treatment groups. One patient treated with Arimidex (Anastrozole) discontinued the trial because of testicular enlargement. The mean baseline-subtracted change in testicular volume after 6 months of treatment was + 6.6 ± 7.9 cm in the Arimidex (Anastrozole) -treated patients and + 5.2 ± 8.0 cm in the placebo group.
McCune-Albright Syndrome Study
A multi-center, single-arm, open-label study was conducted in 28 girls with McCune-Albright Syndrome and progressive precocious puberty aged 2 to
Five patients (18%) experienced adverse reactions that were considered possibly related to Arimidex (Anastrozole) . These were nausea, acne, pain in an extremity, increased alanine transaminase and aspartate transaminase, and allergic dermatitis.
Pharmacokinetics in Pediatric Patients
Following 1 mg once daily multiple administration in pediatric patients, the mean time to reach the maximum anastrozole concentration was 1 hr. The mean (range) disposition parameters of anastrozole in pediatric patients were described by a CL/F of 1.54 L/h (0.77-4.53 L/h) and V/F of 98.4 L (50.7-330.0 L). The terminal elimination half-life was 46.8 h, which was similar to that observed in postmenopausal women treated with anastrozole for breast cancer. Based on a population pharmacokinetic analysis, the pharmacokinetics of anastrozole was similar in boys with pubertal gynecomastia and girls with McCune-Albright Syndrome.
In studies 0030 and 0027, about 50% of patients were 65 or older. Patients ≥ 65 years of age had moderately better tumor response and time to tumor progression than patients
In the ATAC study, 45% of patients were 65 years of age or older. The efficacy of Arimidex (Anastrozole) compared to tamoxifen in patients who were 65 years or older (N=1413 for Arimidex (Anastrozole) and N=1410 for tamoxifen, the hazard ratio for disease-free survival was 0.93 [95% CI: 0.80, 1.08]) was less than efficacy observed in patients who were less than 65 years of age (N=1712 for Arimidex (Anastrozole) and N=1706 for tamoxifen, the hazard ratio for disease-free survival was 0.79 [95% CI: 0.67, 0.94]).
The pharmacokinetics of anastrozole are not affected by age.
Arimidex (Anastrozole) Overdosage
Clinical trials have been conducted with Arimidex (Anastrozole) , up to 60 mg in a single dose given to healthy male volunteers and up to 10 mg daily given to postmenopausal women with advanced breast cancer; these dosages were tolerated. A single dose of Arimidex (Anastrozole) that results in life-threatening symptoms has not been established. There is no specific antidote to overdosage and treatment must be symptomatic. In the management of an overdose, consider that multiple agents may have been taken. Vomiting may be induced if the patient is alert. Dialysis may be helpful because Arimidex (Anastrozole) is not highly protein bound. General supportive care, including frequent monitoring of vital signs and close observation of the patient, is indicated.
Arimidex (Anastrozole) Description
Arimidex (Anastrozole) tablets for oral administration contain 1 mg of anastrozole, a non-steroidal aromatase inhibitor. It is chemically described as 1,3-Benzenediacetonitrile, a, a, a', a'-tetramethyl-5-(1H-1,2,4-triazol-1-ylmethyl). Its molecular formula is CHN and its structural formula is:
Anastrozole is an off-white powder with a molecular weight of 293.4. Anastrozole has moderate aqueous solubility (0.5 mg/mL at 25°C); solubility is independent of pH in the physiological range. Anastrozole is freely soluble in methanol, acetone, ethanol, and tetrahydrofuran, and very soluble in acetonitrile.
Each tablet contains as inactive ingredients: lactose, magnesium stearate, hydroxypropylmethylcellulose, polyethylene glycol, povidone, sodium starch glycolate, and titanium dioxide.
Arimidex (Anastrozole) Clinical Pharmacology
The growth of many cancers of the breast is stimulated or maintained by estrogens.
In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues and in the cancer tissue itself can therefore be achieved by specifically inhibiting the aromatase enzyme.
Anastrozole is a selective non-steroidal aromatase inhibitor. It significantly lowers serum estradiol concentrations and has no detectable effect on formation of adrenal corticosteroids or aldosterone.
Arimidex (Anastrozole) Nonclinical Toxicology
A conventional carcinogenesis study in rats at doses of 1.0 to 25 mg/kg/day (about 10 to 243 times the daily maximum recommended human dose on a mg/m basis) administered by oral gavage for up to 2 years revealed an increase in the incidence of hepatocellular adenoma and carcinoma and uterine stromal polyps in females and thyroid adenoma in males at the high dose. A dose-related increase was observed in the incidence of ovarian and uterine hyperplasia in females. At 25 mg/kg/day, plasma AUC levels in rats were 110 to 125 times higher than the level exhibited in postmenopausal volunteers at the recommended dose. A separate carcinogenicity study in mice at oral doses of 5 to 50 mg/kg/day (about 24 to 243 times the daily maximum recommended human dose on a mg/m basis) for up to 2 years produced an increase in the incidence of benign ovarian stromal, epithelial and granulosa cell tumors at all dose levels. A dose-related increase in the incidence of ovarian hyperplasia was also observed in female mice. These ovarian changes are considered to be rodent-specific effects of aromatase inhibition and are of questionable significance to humans. The incidence of lymphosarcoma was increased in males and females at the high dose. At 50 mg/kg/day, plasma AUC levels in mice were 35 to 40 times higher than the level exhibited in postmenopausal volunteers at the recommended dose.
Arimidex (Anastrozole) has not been shown to be mutagenic in tests (Ames and E. coli bacterial tests, CHO-K1 gene mutation assay) or clastogenic either (chromosome aberrations in human lymphocytes) or (micronucleus test in rats).
Oral administration of anastrozole to female rats (from 2 weeks before mating to pregnancy day 7) produced significant incidence of infertility and reduced numbers of viable pregnancies at 1 mg/kg/day (about 10 times the recommended human dose on a mg/m basis and 9 times higher than the AUC found in postmenopausal volunteers at the recommended dose). Pre-implantation loss of ova or fetus was increased at doses equal to or greater than 0.02 mg/kg/day (about one-fifth the recommended human dose on a mg/m basis). Recovery of fertility was observed following a 5-week non-dosing period which followed 3 weeks of dosing. It is not known whether these effects observed in female rats are indicative of impaired fertility in humans.
Multiple-dose studies in rats administered anastrozole for 6 months at doses equal to or greater than 1 mg/kg/day (which produced plasma anastrozole C and AUC that were 19 and 9 times higher than the respective values found in postmenopausal volunteers at the recommended dose) resulted in hypertrophy of the ovaries and the presence of follicular cysts. In addition, hyperplastic uteri were observed in 6-month studies in female dogs administered doses equal to or greater than 1 mg/kg/day (which produced plasma anastrozole C and AUC that were 22 times and 16 times higher than the respective values found in postmenopausal women at the recommended dose). It is not known whether these effects on the reproductive organs of animals are associated with impaired fertility in premenopausal women.
Reproductive Toxicology
Anastrozole has been found to cross the placenta following oral administration of 0.1 mg/kg in rats and rabbits (about 1 and 1.9 times the recommended human dose, respectively, on a mg/m basis). Studies in both rats and rabbits at doses equal to or greater than 0.1 and 0.02 mg/kg/day, respectively (about 1 and 1/3, respectively, the recommended human dose on a mg/m basis), administered during the period of organogenesis showed that anastrozole increased pregnancy loss (increased pre- and/or post-implantation loss, increased resorption, and decreased numbers of live fetuses); effects were dose related in rats. Placental weights were significantly increased in rats at doses of 0.1 mg/kg/day or more.
Evidence of fetotoxicity, including delayed fetal development (i.e., incomplete ossification and depressed fetal body weights), was observed in rats administered doses of 1 mg/kg/day (which produced plasma anastrozole C and AUC that were 19 times and 9 times higher than the respective values found in postmenopausal volunteers at the recommended dose). There was no evidence of teratogenicity in rats administered doses up to 1.0 mg/kg/day. In rabbits, anastrozole caused pregnancy failure at doses equal to or greater than 1.0 mg/kg/day (about 16 times the recommended human dose on a mg/m basis); there was no evidence of teratogenicity in rabbits administered 0.2 mg/kg/day (about 3 times the recommended human dose on a mg/m basis).
Arimidex (Anastrozole) Clinical Studies
A multicenter, double-blind trial (ATAC) randomized 9,366 postmenopausal women with operable breast cancer to adjuvant treatment with Arimidex (Anastrozole) 1 mg daily, tamoxifen 20 mg daily, or a combination of the two treatments for five years or until recurrence of the disease.
The primary endpoint of the trial was disease-free survival (i.e., time to occurrence of a distant or local recurrence, or contralateral breast cancer or death from any cause). Secondary endpoints of the trial included distant disease-free survival, the incidence of contralateral breast cancer and overall survival. At a median follow-up of 33 months, the combination of Arimidex (Anastrozole) and tamoxifen did not demonstrate any efficacy benefit when compared with tamoxifen in all patients as well as in the hormone receptor positive subpopulation. This treatment arm was discontinued from the trial. Based on clinical and pharmacokinetic results from the ATAC trial, tamoxifen should not be administered with anastrozole [see ].
Demographic and other baseline characteristics were similar among the three treatment groups (see Table ).
Patients in the two monotherapy arms of the ATAC trial were treated for a median of 60 months (5 years) and followed for a median of 68 months. Disease-free survival in the intent-to-treat population was statistically significantly improved [Hazard Ratio (HR) = 0.87, 95% CI: 0.78, 0.97, p=0.0127] in the Arimidex (Anastrozole) arm compared to the tamoxifen arm. In the hormone receptor-positive subpopulation representing about 84% of the trial patients, disease-free survival was also statistically significantly improved (HR = 0.83, 95% CI: 0.73, 0.94, p=0.0049) in the Arimidex (Anastrozole) arm compared to the tamoxifen arm.
Figure 1 — Disease-Free Survival Kaplan Meier Survival Curve for all Patients Randomized to Arimidex (Anastrozole) or Tamoxifen Monotherapy in the ATAC trial (Intent-to-Treat)
Figure 2 — Disease-free Survival for Hormone Receptor-Positive Subpopulation of Patients Randomized to Arimidex (Anastrozole) or Tamoxifen Monotherapy in the ATAC Trial
The survival data with 68 months follow-up is presented in Table 9.
In the group of patients who had previous adjuvant chemotherapy (N=698 for Arimidex (Anastrozole) and N=647 for tamoxifen), the hazard ratio for disease-free survival was 0.91 (95% CI: 0.73 to 1.13) in the Arimidex (Anastrozole) arm compared to the tamoxifen arm.
The frequency of individual events in the intent-to-treat population and the hormone receptor-positive subpopulation are described in Table 8.
A summary of the study efficacy results is provided in Table 9.
10-year median follow-up Efficacy Results from the ATAC Trial
In a subsequent analysis of the ATAC trial, patients in the two monotherapy arms were followed for a median of 120 months (10 years). Patients received study treatment for a median of 60 months (5 years) (see Table 10).
Figure 3 - Disease-Free Survival Kaplan Meier Survival Curve for all Patients Randomized to Arimidex (Anastrozole) or Tamoxifen Monotherapy in the ATAC Trial (Intent-to-Treat)
a
Figure 4 - Disease-Free Survival for Hormone Receptor-Positive Subpopulation of Patients Randomized to Arimidex (Anastrozole) or Tamoxifen Monotherapy in the ATAC Trial
b
Two double-blind, controlled clinical studies of similar design (0030, a North American study and 0027, a predominately European study) were conducted to assess the efficacy of Arimidex (Anastrozole) compared with tamoxifen as first-line therapy for hormone receptor positive or hormone receptor unknown locally advanced or metastatic breast cancer in postmenopausal women. A total of 1021 patients between the ages of 30 and 92 years old were randomized to receive trial treatment. Patients were randomized to receive 1 mg of Arimidex (Anastrozole) once daily or 20 mg of tamoxifen once daily. The primary endpoints for both trials were time to tumor progression, objective tumor response rate, and safety.
Demographics and other baseline characteristics, including patients who had measurable and no measurable disease, patients who were given previous adjuvant therapy, the site of metastatic disease and ethnic origin were similar for the two treatment groups for both trials. The following table summarizes the hormone receptor status at entry for all randomized patients in trials 0030 and 0027.
For the primary endpoints, trial 0030 showed that Arimidex (Anastrozole) had a statistically significant advantage over tamoxifen (p=0.006) for time to tumor progression; objective tumor response rates were similar for Arimidex (Anastrozole) and tamoxifen. Trial 0027 showed that Arimidex (Anastrozole) and tamoxifen had similar objective tumor response rates and time to tumor progression (see Table and Figures and ).
Table 12 below summarizes the results of trial 0030 and trial 0027 for the primary efficacy endpoints.
Figure 5 - Kaplan-Meier probability of time to disease progression for all randomized patients (intent-to-treat) in Trial 0030
Figure 6 - Kaplan-Meier probability of time to progression for all randomized patients (intent-to-treat) in Trial 0027
Results from the secondary endpoints were supportive of the results of the primary efficacy endpoints. There were too few deaths occurring across treatment groups of both trials to draw conclusions on overall survival differences.
Anastrozole was studied in two controlled clinical trials (0004, a North American study; 0005, a predominately European study) in postmenopausal women with advanced breast cancer who had disease progression following tamoxifen therapy for either advanced or early breast cancer. Some of the patients had also received previous cytotoxic treatment. Most patients were ER-positive; a smaller fraction were ER-unknown or ER-negative; the ER-negative patients were eligible only if they had had a positive response to tamoxifen. Eligible patients with measurable and non-measurable disease were randomized to receive either a single daily dose of 1 mg or 10 mg of Arimidex (Anastrozole) or megestrol acetate 40 mg four times a day. The studies were double-blinded with respect to Arimidex (Anastrozole) . Time to progression and objective response (only patients with measurable disease could be considered partial responders) rates were the primary efficacy variables. Objective response rates were calculated based on the Union Internationale Contre le Cancer (UICC) criteria. The rate of prolonged (more than 24 weeks) stable disease, the rate of progression, and survival were also calculated.
Both trials included over 375 patients; demographics and other baseline characteristics were similar for the three treatment groups in each trial. Patients in the 0005 trial had responded better to prior tamoxifen treatment. Of the patients entered who had prior tamoxifen therapy for advanced disease (58% in Trial 0004; 57% in Trial 0005), 18% of these patients in Trial 0004 and 42% in Trial 0005 were reported by the primary investigator to have responded. In Trial 0004, 81% of patients were ER-positive, 13% were ER-unknown, and 6% were ER-negative. In Trial 0005, 58% of patients were ER-positive, 37% were ER-unknown, and 5% were ER-negative. In Trial 0004, 62% of patients had measurable disease compared to 79% in Trial 0005. The sites of metastatic disease were similar among treatment groups for each trial. On average, 40% of the patients had soft tissue metastases; 60% had bone metastases; and 40% had visceral (15% liver) metastases.
Efficacy results from the two studies were similar as presented in Table 13. In both studies there were no significant differences between treatment arms with respect to any of the efficacy parameters listed in the table below.
When data from the two controlled trials are pooled, the objective response rates and median times to progression and death were similar for patients randomized to Arimidex (Anastrozole) 1 mg and megestrol acetate. There is, in this data, no indication that Arimidex (Anastrozole) 10 mg is superior to Arimidex (Anastrozole) 1 mg.
Arimidex (Anastrozole) How Supplied/storage And Handling
These tablets are supplied in bottles of 30 tablets (NDC 0310-0201-30).
Arimidex (Anastrozole) Patient Counseling Information
Arimidex (Anastrozole)
