Name: Letrozole
Brand: Selleck Chemicals
SKU: S1235
Rating: 5 (38 reviews)

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Quality Control

Batch: Purity: 99.99%

99.99

Related Targets	Adrenergic Receptor Estrogen/progestogen Receptor GPR Androgen Receptor Glucocorticoid Receptor ACE RAAS Progesterone Receptor Opioid Receptor PGES
Other Aromatase Inhibitors	Obacunone (AI3-37934) Fadrozole (CGS16949A) alpha-Naphthoflavone

Cell Culture, Treatment & Working Concentration

Cell Lines	Assay Type	Concentration	Incubation Time	Activity Description	PMID
JEG3	Function assay			Inhibition of aromatase activity in human JEG3 cells, IC50=0.00089μM	18590272
JEG3	Function assay			Inhibition of aromatase in human JEG3 cells by scintillation spectrometry, IC50=0.00089μM	20148564
MDA-MB-435	Growth inhibition assay		48 hrs	Growth inhibition of human MDA-MB-435 cells after 48 hrs by sulforhodamine B assay, GI50=0.067μM	20950898
IGROV1	Growth inhibition assay		48 hrs	Growth inhibition of human IGROV1 cells after 48 hrs by sulforhodamine B assay, GI50=0.095μM	20950898
MDA-MB-231	Growth inhibition assay		48 hrs	Growth inhibition of human MDA-MB-231cells after 48 hrs by sulforhodamine B assay, GI50=0.15μM	20950898
T47D	Growth inhibition assay		48 hrs	Growth inhibition of human T47D cells after 48 hrs by sulforhodamine B assay, GI50=0.44μM	20950898
MCF7	Growth inhibition assay		48 hrs	Growth inhibition of human MCF7 cells after 48 hrs by sulforhodamine B assay, GI50=0.7μM	20950898
OVCAR4	Growth inhibition assay		48 hrs	Growth inhibition of human OVCAR4 cells after 48 hrs by sulforhodamine B assay, GI50=0.88μM	20950898
BT549	Growth inhibition assay		48 hrs	Growth inhibition of human BT549 cells after 48 hrs by sulforhodamine B assay, GI50=0.89μM	20950898
SKOV3	Growth inhibition assay		48 hrs	Growth inhibition of human SKOV3 cells after 48 hrs by sulforhodamine B assay, GI50=1.09μM	20950898
NCI/ADR-RES	Growth inhibition assay		48 hrs	Growth inhibition of human NCI/ADR-RES cells after 48 hrs by sulforhodamine B assay, GI50=1.16μM	20950898
MDA-N	Growth inhibition assay		48 hrs	Growth inhibition of human MDA-N cells after 48 hrs by sulforhodamine B assay, GI50=1.61μM	20950898
OVCAR5	Growth inhibition assay		48 hrs	Growth inhibition of human OVCAR5 cells after 48 hrs by sulforhodamine B assay, GI50=1.62μM	20950898
Hs 578T	Growth inhibition assay		48 hrs	Growth inhibition of human Hs 578T cells after 48 hrs by sulforhodamine B assay, GI50=2.17μM	20950898
OVCAR8	Growth inhibition assay		48 hrs	Growth inhibition of human OVCAR8 cells after 48 hrs by sulforhodamine B assay, GI50=4.5μM	20950898
OVCAR3	Growth inhibition assay		48 hrs	Growth inhibition of human OVCAR3 cells after 48 hrs by sulforhodamine B assay, GI50=5.87μM	20950898
MCF7a	Cytotoxicity assay		10 days	Cytotoxicity against human MCF7a cells expressing Tet-off-3betaHSD1-Arom assessed as inhibition of TST-stimulated cell proliferation measured after 10 days, EC50=0.000004μM	22951074
V79MZh	Function assay			Inhibition of human CYP11B2 expressed in hamster V79MZh cells using [1,2-3H]-11-deoxy-corticosterone as substrate, IC50=1.42μM	23281812
V79MZh	Function assay			Inhibition of human CYP11B1 expressed in hamster V79MZh cells using [1,2-3H]-11-deoxy-corticosterone as substrate, IC50=2.62μM	23281812
H295R	Function assay	5 uM	24 hrs	Inhibition of CYP19 in human H295R cells using [1beta-3H(N)]-androst-4-ene-3,17-dione at 5 uM after 24 hrs by tritiated water release assay	24025069
MCF7	Cytotoxicity assay		72 hrs	Cytotoxicity against estrogen-dependent human MCF7 cells after 72 hrs by MTT assay, IC50=0.007μM	24345481
MCF7	Cytotoxicity assay		24 to 96 hrs	Cytotoxicity against human MCF7 cells after 24 to 96 hrs, IC50=0.02μM	24345481
JEG-3	Function assay			Inhibition of aromatase (unknown origin) expressed in JEG-3 cells, IC50=0.00089μM	25992880
insect cells	Function assay		30 mins	Inhibition of recombinant human CYP19 expressed in baculovirus infected insect cells using MFC as substrate measured after 30 mins by fluorometric analysis, IC50=0.0053μM	27647367
T47D	Function assay		24 hrs	Inhibition of aromatase activity in human T47D cells after 24 hrs, IC50=29.5μM	27770735
T47D	Function assay		24 hrs	Inhibition of aromatase activity in human T47D cells after 24 hrs, IC50=29.5μM	28427017
MCF7	Cytotoxicity assay		48 hrs	Cytotoxicity against human MCF7 cells after 48 hrs by MTT assay, IC50=4.73μM	29202405
MCF7	Growth inhibition assay		72 hrs	Growth inhibition of human MCF7 cells incubated for 72 hrs by cell counting based method, GI50=4.1μM	30822713
MDA-MB-231	Growth inhibition assay		72 hrs	Growth inhibition of human MDA-MB-231 cells incubated for 72 hrs by cell counting based method, GI50=10μM	30822713
insect cells	Function assay			Inhibition of recombinant human aromatase expressed in baculovirus infected insect cells using O-benzyl fluorescein benzyl ester as substrate in presence of NADPH generating system by fluorescence based analysis, IC50=0.0019μM	31416738
MCF-7aro	Function assay		1 hr	Inhibition of aromatase in human MCF-7aro cells using [1beta-3H] androstenedione as substrate incubated for 1 hr by liquid scintillation counting method, IC50=0.0019μM	31732252
insect cells	Function assay		30 mins	Inhibition of human recombinant aromatase expressed in baculovirus infected insect cells using O-benzylfluorescein benzyl ester as substrate after 30 mins, IC50=0.0011μM	ChEMBL
Click to View More Cell Line Experimental Data

Chemical Information, Storage & Stability

Molecular Weight	285.3	Formula	C₁₇H₁₁N₅	Storage (From the date of receipt)	3 years-20°Cpowder
CAS No.	112809-51-5	Download SDF		Storage of Stock Solutions	1 year-80°Cin solvent 1 month-20°Cin solvent
Synonyms	CGS 20267			Smiles	C1=CC(=CC=C1C#N)C(C2=CC=C(C=C2)C#N)N3C=NC=N3

Solubility

In vitro
Batch:

DMSO : 57 mg/mL (199.78 mM)
(Moisture-contaminated DMSO may reduce solubility. Use fresh, anhydrous DMSO.)

Water : Insoluble

Ethanol : Insoluble

Molarity Calculator

Mass	Concentration	Volume	Molecular Weight
=	×	×

Dilution Calculator Molecular Weight Calculator

In vivo Batch:
Homogeneous suspension	CMC-NA	≥5mg/ml	Taking the 1 mL working solution as an example, add 5 mg of this product to 1 ml of CMC-Na solution, mix evenly to obtain a homogeneous suspension with a final concentration of 5 mg/ml.
Homogeneous suspension	CMC-NA	≥5mg/ml	Taking the 1 mL working solution as an example, add 5 mg of this product to 1 ml of CMC-Na solution, mix evenly to obtain a homogeneous suspension with a final concentration of 5 mg/ml.
Homogeneous suspension	CMC-NA	≥5mg/ml	Taking the 1 mL working solution as an example, add 5 mg of this product to 1 ml of CMC-Na solution, mix evenly to obtain a homogeneous suspension with a final concentration of 5 mg/ml.
Homogeneous suspension	CMC-NA	≥5mg/ml	Taking the 1 mL working solution as an example, add 5 mg of this product to 1 ml of CMC-Na solution, mix evenly to obtain a homogeneous suspension with a final concentration of 5 mg/ml.
Homogeneous suspension	CMC-NA	≥5mg/ml	Taking the 1 mL working solution as an example, add 5 mg of this product to 1 ml of CMC-Na solution, mix evenly to obtain a homogeneous suspension with a final concentration of 5 mg/ml.
Clear solution	5%DMSO 1 40%PEG300 2 5%Tween80 3 50%ddH2O Validated by Selleck labs. Should you need adjustments to this formulation, contact our sales team for custom testing.	2.850mg/ml (9.99mM)	Taking the 1 mL working solution as an example, add 50 μL of 57 mg/ml clarified DMSO stock solution to 400 μL of PEG300, mix evenly to clarify it; add 50 μL of Tween80 to the above system, mix evenly to clarify; then continue to add 500 μL of ddH2O to adjust the volume to 1 mL. The mixed solution should be used immediately for optimal results.
Clear solution	5% DMSO 1 95% Corn oil Validated by Selleck labs. Should you need adjustments to this formulation, contact our sales team for custom testing.	0.450mg/ml (1.58mM)	Taking the 1 mL working solution as an example, add 50 μL of 9 mg/ml clear DMSO stock solution to 950 μL of corn oil and mix evenly. The mixed solution should be used immediately for optimal results.

In vivo Formulation Calculator (Clear solution)

Step 1: Enter information below (Recommended: An additional animal making an allowance for loss during the experiment)

Dosage: mg/kg Average weight of animals: g Dosing volume per animal:μL Number of animals:

Step 2: Enter the in vivo formulation (This is only the calculator, not formulation. Please contact us first if there is no in vivo formulation at the solubility Section.)

% DMSO + % + % Tween 80 + % ddH₂O

%DMSO+ %

Calculation results:

Working concentration: mg/ml;

Method for preparing DMSO master liquid: mg drug pre-dissolved in μL DMSO ( Master liquid concentration mg/mL, Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug. )

Method for preparing in vivo formulation: Take μL DMSO master liquid, next addμL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH₂O, mix and clarify.

Method for preparing in vivo formulation: Take μL DMSO master liquid, next add μL Corn oil, mix and clarify.

Note: 1. Please make sure the liquid is clear before adding the next solvent.
2. Be sure to add the solvent(s) in order. You must ensure that the solution obtained, in the previous addition, is a clear solution before proceeding to add the next solvent. Physical methods such as vortex, ultrasound or hot water bath can be used to aid dissolving.

Mechanism of Action

Targets/IC₅₀/Ki	Aromatase (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 this compound is calculated to be 1-13 nM. It 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. This chemical 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 this compound did not affect their growth even when high letrozole concentrations (100 nM) or prolonged culture times. Concurrent administration of 17-β-estradiol with it (10 nM) decreased the stimulatory effect of the enzymatic activity of MMP-2 and - 9 released by estradiol.
Kinase Assay	Human placental aromatase activity
Kinase Assay	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.
In vivo	Letrozole inhibits aromatase in vivo with ED50 of 1-3 μg/kg p.o.. This compound displays anti-endocrine effects. It inhibits androstenedione-induced uterine hypertrophy in immature rats with ED50 of 1-3 μg/kg. In the adult female rat, this compound (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. This chemical induces dose-dependent regression of estrogen-dependent, 9,10-dimethylbenz-a-anthracene-induced mammary tumors in adult female rats. The ED50 for it is determined to be 10 - 30 µg/kg/day, with complete inhibition at a daily dose of 10 µg/day. It 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..
References	[1] https://pubmed.ncbi.nlm.nih.gov/14630089/ [2] https://pubmed.ncbi.nlm.nih.gov/2149502/ [3] https://pubmed.ncbi.nlm.nih.gov/12569569/ [4] https://pubmed.ncbi.nlm.nih.gov/20095792/ [5] https://pubmed.ncbi.nlm.nih.gov/7628871/ [6] https://pubmed.ncbi.nlm.nih.gov/2973160/

Clinical Trial Information

(data from https://clinicaltrials.gov, updated on 2024-05-22)

NCT Number	Recruitment	Conditions	Sponsor/Collaborators	Start Date	Phases
NCT06143631	Not yet recruiting	Leiomyoma Uterine\|Leiomyoma\|Fibroid\|Fibroid Uterus	University of California San Francisco\|Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD)	May 13 2024	Phase 4
NCT05872204	Recruiting	Low Grade Serous Ovarian Carcinoma\|Adult Type Granulosa Cell Tumor	Universitaire Ziekenhuizen KU Leuven\|Kom Op Tegen Kanker\|Eli Lilly and Company\|European Network of Gynaecological Oncological Trial Groups (ENGOT)	November 30 2023	Phase 2

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Letrozole Aromatase inhibitor

Chemical Structure

Molecular Weight: 285.3