Letrozole

1 INDICATIONS AND USAGE Letrozole tablet is an aromatase inhibitor indicated for: Adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer ( 1.1 ) Extended adjuvant treatment of postmenopausal women with early breast cancer who have received prior standard adjuvant tamoxifen therapy ( 1.2 ) First and second-line treatment of postmenopausal women with hormone receptor positive or unknown advanced breast cancer ( 1.3 ) 1.1 Adjuvant Treatment of Early Breast Cancer Letrozole tablets are indicated for the adjuvant treatment of postmenopausal women with hormone receptor positive early breast cancer. 1.2 Extended Adjuvant Treatment of Early Breast Cancer Letrozole tablets are indicated for the extended adjuvant treatment of early breast cancer in postmenopausal women, who have received 5 years of adjuvant tamoxifen therapy. The effectiveness of letrozole tablets in extended adjuvant treatment of early breast cancer is based on an analysis of disease-free survival (DFS) in patients treated with letrozole tablets for a median of 60 months [see Clinical Studies ( 14.2 , 14.3 )] . 1.3 First and Second-Line Treatment of Advanced Breast Cancer Letrozole tablets are indicated for first-line treatment of postmenopausal women with hormone receptor positive or unknown, locally advanced or metastatic breast cancer. Letrozole tablets are also indicated for the treatment of advanced breast cancer in postmenopausal women with disease progression following antiestrogen therapy [see Clinical Studies ( 14.4 , 14.5 )].

12.1 Mechanism of Action The growth of some cancers of the breast is stimulated or maintained by estrogens. Treatment of breast cancer thought to be hormonally responsive (i.e., estrogen and/or progesterone receptor positive or receptor unknown) has included a variety of efforts to decrease estrogen levels (ovariectomy, adrenalectomy, hypophysectomy) or inhibit estrogen effects (antiestrogens and progestational agents). These interventions lead to decreased tumor mass or delayed progression of tumor growth in some women. 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. Letrozole is a nonsteroidal competitive inhibitor of the aromatase enzyme system; it inhibits the conversion of androgens to estrogens. In adult nontumor- and tumor-bearing female animals, letrozole is as effective as ovariectomy in reducing uterine weight, elevating serum LH, and causing the regression of estrogen-dependent tumors. In contrast to ovariectomy, treatment with letrozole does not lead to an increase in serum FSH. Letrozole selectively inhibits gonadal steroidogenesis but has no significant effect on adrenal mineralocorticoid or glucocorticoid synthesis. Letrozole inhibits the aromatase enzyme by competitively binding to the heme of the cytochrome P450 subunit of the enzyme, resulting in a reduction of estrogen biosynthesis in all tissues. Treatment of women with letrozole significantly lowers serum estrone, estradiol and estrone sulfate and has not been shown to significantly affect adrenal corticosteroid synthesis, aldosterone synthesis, or synthesis of thyroid hormones.

2 DOSAGE AND ADMINISTRATION Letrozole tablets are taken orally without regard to meals ( 2 ): Recommended dose: 2.5.mg once daily ( 2.1 ) Patients with cirrhosis or severe hepatic impairment: 2.5 mg every other day ( 2.5 , 5.3 ) 2.1 Recommended Dose The recommended dose of letrozole tablet is one 2.5 mg tablet administered once a day, without regard to meals. 2.2 Use in Adjuvant Treatment of Early Breast Cancer In the adjuvant setting, the optimal duration of treatment with letrozole is unknown. In both the adjuvant study and the post approval adjuvant study, median treatment duration was 5 years. Treatment should be discontinued at relapse [see Clinical Studies ( 14.1 )]. 2.3 Use in Extended Adjuvant Treatment of Early Breast Cancer In the extended adjuvant setting, the optimal treatment duration with letrozole tablet is not known. The planned duration of treatment in the study was 5 years. In the final updated analysis, conducted at a median follow-up of 62 months, the median treatment duration for letrozole tablets was 60 months. Seventy-one percent (71%) of patients were treated for at least 3 years and 58% of patients completed at least 4.5 years of extended adjuvant treatment. The treatment should be discontinued at tumor relapse [see Clinical Studies ( 14.2 )]. 2.4 Use in First and Second-Line Treatment of Advanced Breast Cancer In patients with advanced disease, treatment with letrozole tablets should continue until tumor progression is evident [see Clinical Studies ( 14.4 , 14.5 )] . 2.5 Use in Hepatic Impairment No dosage adjustment is recommended for patients with mild to moderate hepatic impairment, although letrozole tablets blood concentrations were modestly increased in subjects with moderate hepatic impairment due to cirrhosis. The dose of letrozole tablets in patients with cirrhosis and severe hepatic dysfunction should be reduced by 50% [see Warnings and Precautions ( 5.3 )]. The recommended dose of letrozole tablets for such patients is 2.5 mg administered every other day. The effect of hepatic impairment on letrozole tablets exposure in noncirrhotic cancer patients with elevated bilirubin levels has not been determined. 2.6 Use in Renal Impairment No dosage adjustment is required for patients with renal impairment if creatinine clearance is greater than or equal to 10 mL/min [see Clinical Pharmacology ( 12.3 )] .

6 ADVERSE REACTIONS The following adverse reactions are discussed in greater detail in other sections of the labeling. Bone effects [see Warnings and Precautions ( 5.1 )] Increases in cholesterol [see Warnings and Precautions ( 5.2 )] Fatigue and Dizziness [see Warnings and Precautions ( 5.4 )] The most common adverse reactions (greater than 20%) were hot flashes, arthralgia; flushing, asthenia, edema, arthralgia, headache, dizziness, hypercholesterolemia, sweating increased, bone pain and musculoskeletal ( 6 ). To report SUSPECTED ADVERSE REACTIONS, contact Accord Healthcare Inc. at 1-866-941-7875 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reactions 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. Adjuvant Treatment of Early Breast Cancer In study, BIG 1 to 98, the median treatment duration of adjuvant treatment was 60 months and the median duration of follow-up for safety was 96 months for patients receiving letrozole and tamoxifen. Certain adverse reactions were prospectively specified for analysis (see Table 1), based on the known pharmacologic properties and side effect profiles of the two drugs. Adverse reactions were analyzed irrespective of whether a symptom was present or absent at baseline. Most adverse reactions reported (approximately 75% of patients who reported AEs) were Grade 1 or Grade 2 applying the Common Toxicity Criteria (CTC) Version 2.0/ Common Terminology Criteria for Adverse Events (CTCAE), Version 3.0. Table 1 describes adverse reactions (Grades 1-4 and Grades 3-4) irrespective of relationship to study treatment in the adjuvant trial for the monotherapy arms analysis (safety population). Table 1: Patients With Adverse Reactions (CTC Grades 1 to 4) in the Adjuvant Study – Monotherapy Arms Analysis (Median Follow-up 96 Months; Median Treatment 60 Months) Grades 1 to 4 Grades 3 to 4 Adverse Reactions Letrozole Tablets N=2448 n (%) Tamoxifen N=2447 n (%) Letrozole Tablets N=2448 n (%) Tamoxifen N=2447 n (%) Patients with any adverse reaction 2309 (93.4) 2212 (90.4) 636 (26.0) 606 (24.8) Hypercholesterolemia * 1280 (52.3) 700 (28.6) 11 ( 0.4) 6 ( 0.2) Hot flashes * 819 (33.5) 929 (38.0) - - - - Arthralgia/Arthritis * 621 (25.4) 504 (20.6) 84 ( 3.4) 50 ( 2.0) Bone fractures 1 361 (14.7) 280 (11.4) - - - - Night sweats * 356 (14.6) 426 (17.4) - - - - Weight Increase * 317 (12.9) 378 (15.4) 27 ( 1.1) 39 ( 1.6) Nausea * 284 (11.6) 277 (11.3) 6 ( 0.2) 9 ( 0.4) Bone Fractures **2 249 (10.2) 175 ( 7.2) - - - - Fatigue (lethargy, malaise, asthenia) **2 235 ( 9.6) 250 (10.2) 6 ( 0.2) 7 ( 0.3) Myalgia * 221 ( 9.0) 212 ( 8.7) 18 ( 0.7) 14 ( 0.6) Vaginal Bleeding * 129 ( 5.3) 320 (13.1) 1 (<0.1) 8 ( 0.3) Edema * 164 ( 6.7) 160 ( 6.5) 3 ( 0.1) 1 (<0.1) Weight decrease 140 ( 5.7) 129 ( 5.3) 8 ( 0.3) 5 ( 0.2) Osteoporosis ** 126 ( 5.1) 66 ( 2.7) 10 ( 0.4) 5 ( 0.2) Back Pain 125 ( 5.1) 136 ( 5.6) 7 ( 0.3) 11 ( 0.4) Bone pain 123 ( 5.0) 109 ( 4.5) 6 ( 0.2) 4 ( 0.2) Depression 119 ( 4.9) 114 ( 4.7) 16 ( 0.7) 14 ( 0.6) Vaginal irritation * 112 ( 4.6) 77 ( 3.1) 2 (<0.1) 2 (<0.1) Headache * 105 ( 4.3) 94 ( 3.8) 8 ( 0.3) 4 ( 0.2) Pain in extremity 103 ( 4.2) 79 ( 3.2) 6 ( 0.2) 4 ( 0.2) Osteopenia * 87 ( 3.6) 76 ( 3.1) 0 - 3 (0.1) Dizziness/Light-Headedness * 84 ( 3.4) 80 ( 3.3) 1 (<0.1) 6 (0.2) Alopecia 83 ( 3.4) 84 ( 3.4) - - - - Vomiting * 80 ( 3.3) 80 ( 3.3) 3 ( 0.1) 5 (0.2) Cataract * 49 ( 2.0) 54 ( 2.2) 16 ( 0.7) 17 ( 0.7) Constipation * 49 ( 2.0) 71 ( 2.9) 3 ( 0.1) 1 (<0.1) Myocardial infarction 1 42 (1.7) 28 (1.1) - - - - Breast pain * 37 ( 1.5) 43 ( 1.8) 1 (<0.1) - - Anorexia * 20 ( 0.8) 20 ( 0.8) 1 (<0.1) 1 (<0.1) Endometrial proliferation disorders * 14 (0.6) 86 (3.5) 0 - 14 (0.6) Ovarian cyst * 11 (0.4) 18 (0.7) 4 (0.2) 4 (0.2) Endometrial hyperplasia/ Cancer **1 11 (0.4) 72 (2

5 WARNINGS AND PRECAUTIONS Decreases in bone mineral density may occur. Consider bone mineral density monitoring ( 5.1 ) Increases in total cholesterol may occur. Consider cholesterol monitoring. ( 5.2 ) Fatigue, dizziness and somnolence may occur. Exercise caution when operating machinery ( 5.4 ) Embryo-Fetal Toxicity: Can cause fetal harm when administered to pregnant women. Obtain a pregnancy test in females of reproductive potential. Advise females of reproductive potential to use effective contraception ( 5.6 , 8.1 , 8.3 ) 5.1 Bone Effects Use of letrozole may cause decreases in bone mineral density (BMD). Consideration should be given to monitoring BMD. Results of a safety study to evaluate safety in the adjuvant setting comparing the effect on lumbar spine (L2-L4) BMD of adjuvant treatment with letrozole to that with tamoxifen showed at 24 months a median decrease in lumbar spine BMD of 4.1% in the letrozole arm compared to a median increase of 0.3% in the tamoxifen arm (difference = 4.4%) ( P <0.0001) [see Adverse Reactions ( 6 )] . Updated results from the BMD substudy (MA-17B) in the extended adjuvant setting demonstrated that at 2 years patients receiving letrozole had a median decrease from baseline of 3.8% in hip BMD compared to a median decrease of 2.0% in the placebo group. The changes from baseline in lumbar spine BMD in letrozole and placebo treated groups were not significantly different [see Adverse Reactions ( 6 )]. In the adjuvant trial (BIG 1 to 98) the incidence of bone fractures at any time after randomization was 14.7% for letrozole and 11.4% for tamoxifen at a median follow-up of 96 months. The incidence of osteoporosis was 5.1% for letrozole and 2.7% for tamoxifen [see Adverse Reactions ( 6 )] . In the extended adjuvant trial (MA-17), the incidence of bone fractures at any time after randomization was 13.3% for letrozole and 7.8% for placebo at a median follow-up of 62 months. The incidence of new osteoporosis was 14.5% for letrozole and 7.8% for placebo [see Adverse Reactions ( 6 )]. 5.2 Cholesterol Consideration should be given to monitoring serum cholesterol. In the adjuvant trial (BIG 1 to 98), hypercholesterolemia was reported in 52.3% of letrozole patients and 28.6% of tamoxifen patients. Grade 3 to 4 hypercholesterolemia was reported in 0.4% of letrozole patients and 0.1% of tamoxifen patients. Also in the adjuvant setting, an increase of greater than or equal to 1.5 x upper limit of normal (ULN) in total cholesterol (generally nonfasting) was observed in patients on monotherapy who had baseline total serum cholesterol within the normal range (i.e., less than=1.5 x ULN) in 155/1843 (8.4%) patients on letrozole vs 71/1840 (3.9%) patients on tamoxifen. Lipid lowering medications were required for 29% of patients on letrozole and 20% on tamoxifen [see Adverse Reactions ( 6 )]. 5.3 Hepatic Impairment Subjects with cirrhosis and severe hepatic impairment who were dosed with 2.5 mg of letrozole experienced approximately twice the exposure to letrozole as healthy volunteers with normal liver function [see Clinical Pharmacology ( 12.3 )] . Therefore, a dose reduction is recommended for this patient population. The effect of hepatic impairment on letrozole exposure in cancer patients with elevated bilirubin levels has not been determined [see Dosage and Administration ( 2.5 )]. 5.4 Fatigue and Dizziness Because fatigue, dizziness, and somnolence have been reported with the use of letrozole, caution is advised when driving or using machinery until it is known how the patient reacts to letrozole use. 5.5 Laboratory Test Abnormalities No dose-related effect of letrozole on any hematologic or clinical chemistry parameter was evident. Moderate decreases in lymphocyte counts, of uncertain clinical significance, were observed in some patients receiving letrozole 2.5 mg. This depression was transient in about half of those affected. Two patients on letrozole developed thrombocytopenia; relationship to the stud

4 CONTRAINDICATIONS Pregnancy: Letrozole can cause fetal harm [see Use in Specific Populations ( 8.1 )] . Pregnancy: Letrozole can cause fetal harm [see Use in Specific Populations ( 8.1 )] . Known hypersensitivity to the active substance, or to any of the excipients [see Adverse Reactions ( 6 )] . Known hypersensitivity to the active substance, or to any of the excipients [see Adverse Reactions ( 6 )] . Pregnancy ( 4 ) Known hypersensitivity to the active substance, or to any of the excipients ( 4 )

10 OVERDOSAGE Isolated cases of letrozole overdose have been reported. In these instances, the highest single dose ingested was 62.5 mg or 25 tablets. While no serious adverse reactions were reported in these cases, because of the limited data available, no firm recommendations for treatment can be made. However, emesis could be induced if the patient is alert. In general, supportive care and frequent monitoring of vital signs are also appropriate. In single-dose studies, the highest dose used was 30 mg, which was well tolerated; in multiple-dose trials, the largest dose of 10 mg was well tolerated. Lethality was observed in mice and rats following single oral doses that were equal to or greater than 2,000 mg/kg (about 4,000 to 8,000 times the daily maximum recommended human dose on a mg/m 2 basis); death was associated with reduced motor activity, ataxia and dyspnea. Lethality was observed in cats following single IV doses that were equal to or greater than 10 mg/kg (about 50 times the daily maximum recommended human dose on a mg/m 2 basis); death was preceded by depressed blood pressure and arrhythmias.