Letrozole

Catalog No.S1235 Synonyms: CGS 20267

Letrozole Chemical Structure

Molecular Weight(MW): 285.3

Letrozole is a third generation inhibitor of aromatase with IC50 of 0.07-20 nM in cell-free assays.

Size Price Stock Quantity  
In DMSO USD 480 In stock
USD 97 In stock
USD 170 In stock
USD 470 In stock

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2 Customer Reviews

  • 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.

    Endocrinology 2013 154, 2296-307. Letrozole purchased from Selleck.

    Uterus from mice treated with Letrozole. (A) 13 weeks old aP2-Cre/ERαflox/flox mice treated with vehicle have swollen abdomen while littermates treated with Letrozole for 17 days looks normal (B). (C) Uterus from vehicle treated aP2-/ERαflox/flox mice with severe hydrometra. (D) Uterus from Letrozole treated aP2-Cre/ERαflox/flox mice looks normal.

    PLoS One 2014 9(1), e85581. Letrozole purchased from Selleck.

Purity & Quality Control

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Notes:

2. For more details, such as half maximal inhibitory concentrations (IC50s) and working concentrations of each inhibitor, please click on the link of the inhibitor of interest.
3. "+" indicates inhibitory effect. Increased inhibition is marked by a higher "+" designation.
4. Orange "√" refers to compounds which do inhibitory effects on the related isoform, but without specific value.

Biological Activity

Description Letrozole is a third generation inhibitor of aromatase with IC50 of 0.07-20 nM in cell-free assays.
Targets
Aromatase [1]
(Cell-free assay)
0.07 nM-20 nM
In vitro

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 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]

Protocol

Kinase Assay:[6]
+ Expand

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.
Cell Research:[3]
+ Expand
  • Cell lines: Human breast cancer cells MCF-7
  • Concentrations: ~100 nM
  • Incubation Time: 1 days
  • Method: 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.
    (Only for Reference)
Animal Research:[5]
+ Expand
  • Animal Models: Human breast carcinoma xenografts MCF-7 with human aromatase gene (MCF-7Ca)
  • Formulation: 0.5% (w/v) solution of carboxymethylcellulos
  • Dosages: 20 mg/kg/day
  • Administration: orally administered by gavage once every 2 days
    (Only for Reference)

Solubility (25°C)

In vitro DMSO 57 mg/mL (199.78 mM)
Water <1 mg/mL
Ethanol <1 mg/mL
In vivo 0.5% CMC 10 mg/mL

* 1 mg/ml means slightly soluble or insoluble.
* Please note that Selleck tests the solubility of all compounds in-house, and the actual solubility may differ slightly from published values. This is normal and is due to slight batch-to-batch variations.

Chemical Information

Molecular Weight 285.3
Formula

C17H11N5

CAS No. 112809-51-5
Storage powder
in solvent
Synonyms CGS 20267

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Clinical Trial Information

NCT Number Recruitment Conditions Sponsor/Collaborators Start Date Phases
NCT02941926 Recruiting Breast Cancer Novartis Pharmaceuticals|Novartis November 30, 2016 Phase 3
NCT00006174 Completed McCune Albright Syndrome|Polyostotic Fibrous Dysplasia|Precocious Puberty National Institute of Dental and Craniofacial Research (NIDCR)|National Institutes of Health Clinical Center (CC) August 3, 2000 Phase 1
NCT03007979 Not yet recruiting Breast Cancer|Breast Carcinoma|Cancer of Breast|Malignant Tumor of Breast Washington University School of Medicine February 28, 2017 Phase 2
NCT02907918 Not yet recruiting Breast Cancer|Cancer of Breast|Breast Carcinoma Washington University School of Medicine|Pfizer February 28, 2017 Phase 2
NCT01872260 Recruiting Breast Cancer Novartis Pharmaceuticals|Novartis October 22, 2013 Phase 1
NCT03008408 Not yet recruiting Malignant Neoplasms of Female Genital Organs|Endometrial Carcinoma M.D. Anderson Cancer Center|Novartis April 2017 Phase 2

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Aromatase Signaling Pathway Map

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