Letrozole is a nonsteroidal aromatase inhibitor with IC50 of 11.5 nM, selectively inhibits estrogen biosynthesis, but not progesterone, corticosterone or aldosterone production, provides treatment for breast cancer. Phase 3.

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Letrozole 化学構造
分子量: 285.3



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情報 Letrozole is a nonsteroidal aromatase inhibitor with IC50 of 11.5 nM, selectively inhibits estrogen biosynthesis, but not progesterone, corticosterone or aldosterone production, provides treatment for breast cancer. Phase 3.
目標 Aromatase
IC50 0.07 - 20 nM [1]
In vitro試験 Letrozole potently inhibits aromatase derived from a variety of different sources including human placental microsomes, particulate fractions of human breast cancer, rat ovarian microsomes, MCF-7 cells transfected with aromatase (MCF-7Ca), JEG-3 human choriocarcinoma cells , CHO cells, hamster ovarian tissue, and particulate fractions of human breast cancer with IC50 of 11, 2, 7, 0.07, 0.07, 1.4, 20 and 0.8 nM. In the non-cellular systems, the IC50 of letrozole is calculated to be 1-13 nM. [1] Letrozole maximally inhibits estradiol production in vitro in LH-stimulated hamster ovarian tissue at 0.1 μM with an IC50 of 0.02 μM and does not significantly affect progesterone production up to 350 μM. In ACTH-stimulated rat adrenal tissue in vitro, aldosterone production is inhibited by with an IC50 of 210 μM. [2] Letrozole inhibits growth of the MCF-7 epithelial breast cancer cells in a dose-dependent way with IC50 of 1 nM. Inhibition can be observesed even at the very low concentrations tested (0.1 nM). Treatment of normal MCF-12A epithelial cells with letrozole did not affect their growth even when high letrozole concentrations (100 nM) or prolonged culture times. Letrozole (10 nM) significantly suppressed the stimulatory effects of 4-androstene-3,17-dione (100 nM) or testosterone (100 nM) on MCF-7 cell proliferation. Concurrent administration of 17-β-estradiol with letrozole (10 nM) decreased the stimulatory effect of the enzymatic activity of MMP-2 and - 9 released by estradiol. [3]
In vivo試験 Letrozole inhibits aromatase in vivo with ED50 of 1-3 μg/kg p.o.. [2] Letrozole displays anti-endocrine effects. Letrozole inhibits androstenedione-induced uterine hypertrophy in immature rats with ED50 of 1-3 μg/kg. In the adult female rat, Letrozole (0.3-1 mg/kg daily p.o., 14 days) completely interrupts ovarian cyclicity and reduces uterine weight and serum estradiol (E2) concentrations to a similar extent to that seen after ovariectomy. [1] Letrozole induces dose-dependent regression of estrogen-dependent, 9,10-dimethylbenz-a-anthracene (DMBA)-induced mammary tumors in adult female rats. The ED50 for Letrozole is determined to be 10 - 30 µg/kg/day, with complete inhibition at a daily dose of 10 µg/day. [4] Letrozole produces dose-dependent inhibition of tumor growth of MCF-7 cells transfected with human aromatase gene (MCF-7Ca) implanted athymic nude mice, with complete inhibition at 20 mg/kg per day p.o.. [5]
臨床試験 A phase I trial of Letrozole in postmenopausal women at high risk for breast cancer is currently in recruiting.

推薦された実験操作 (公開の文献だけ)

キナーゼアッセイ: [6]

Human placental aromatase activity The assay is performed in a total volume of 1 mL at 37 ℃. Unless otherwise noted, the incubation mixture contains 11 nM [4- 14C] androstene-3, 17-dione ([4- 14C]A), 24 mM NADPH (tetrasodium salt Type III), the appropriate concentrations of the desired inhibitor, and 120 μg of microsomal protein. The (4- 14C)A is added as a solution in 1.7% ethanol in 0.05 M potassium phosphate buffer (pH 7.4), so that the final concentration of ethanol does not exceed 0.02% (v/v). The reaction is started by the addition of enzyme and stopped after 20 min by the addition of 7 vol of ethyl acetate. The mixture is agitated on a vortex mixer and centrifuged at 600 g for 5 min. The aqueous phase is re-extracted with 7 vol of ethyl acetate, and the combined extracts are evaporated to dryness using an Evapo-Mix. Over 99% of the radio- active of [4- 14C] added is recovered using this extraction system. The residue obtained is dissolved in 150 μL acetone, and 100 μL aliquots are chromatographed for 65 min on thin-layer plates precoated with silica gel 60 using ethyl: acetate: isooctane (140:60, v/v; system A) or toluene: chloroform: methanol (70:140:20; system B). The radioactive zones of the plate are located with a Berthold LB 2760 thin-layer scanner. The radioactive estradiol (E2) and estrone (E1) neaks are identified by comparison with authentic standards. The corresponding bonding band of silica gel is transferred to vials containing 10 mL of scintillation fluid, and counted with a 6880 Liquid Scintillation system.

細胞アッセイ: [3]

細胞系 Human breast cancer cells MCF-7
濃度 ~100 nM
処理時間 1 days
方法 Cells are seeded in duplicate at 5,000 to 10,000 cells per well in 24-well plates. The day after plating, different concentrations of Letrozole are added. At the end of incubation, cells are trypsinizated and placed in Isotone solution and counted immediately using a Coulter particle-counter.

動物実験: [5]

動物モデル Human breast carcinoma xenografts MCF-7 with human aromatase gene (MCF-7Ca)
製剤 0.5% (w/v) solution of carboxymethylcellulos
投薬量 20 mg/kg/day
管理 orally administered by gavage once every 2 days



Download Letrozole SDF
分子量 285.3


CAS No. 112809-51-5
別名 Femara, Piroxicam
溶解度 (25°C)
  • DMSO 57 mg/mL
  • 水 <1 mg/mL
  • エタノール <1 mg/mL
保管 2年 -20°C
6月-80°Cin DMSO


カスタマーレビュー (1)

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Source , , Endocrinology. 2013 Jul;154(7):2296-307 . Letrozole purchased from Selleck
Method Immunohistochemistry
Cell Lines LNCaP tumor xenografts
Concentrations 10 mg/kg body weight
Incubation Time 2 d
Results Effect of aromatase inhibitor letrozole on cellular proliferation marker Ki-67 expression in LNCaP tumor xenografts. A, Ki-67 immunostaining in transverse sections of xenograft tumors from C, C+T, C+T+D, C+T+L, and C+T+D+L mice 2 days after testosterone replacement. Panel B, Quantification of Ki-67–positive cells in LNCaP tumors at day 2 post testosterone replacement. Error bars represent SEM. Number of animals in each group is shown in parentheses. ***, P <.0001.

製品表彰状 (3)

  • 5α-Reductase Inhibition Suppresses Testosterone-Induced Initial Regrowth of Regressed Xenograft Prostate Tumors in Animal Models. [Masoodi KZ, et al. Endocrinology 2013;154(7):2296-307]

    PubMed: 23671262
  • AroER Tri-Screen™ is a Biologically Relevant Assay for Endocrine Disrupting Chemicals Modulating the Activity of Aromatase and/or the Estrogen Receptor [Chen S Toxicol Sci 2014;10.1093/toxsci/kfu023]

    PubMed: 24496634
  • aP2-Cre-Mediated Inactivation of Estrogen Receptor Alpha Causes Hydrometra. [Antonson P, et al. PLoS One 2013;9(1):e85581]

    PubMed: 24416430



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