Indications and uses Pharmacokinetics Side effects
ChemicalBook > CAS DataBase List > Letrozole

Letrozole

Indications and uses Pharmacokinetics Side effects
Product Name
Letrozole
CAS No.
112809-51-5
Chemical Name
Letrozole
Synonyms
LETROZOL;FEMARA;LETRAZOLE;LetrozoleUsp28;Letrozole(FeMara);Letroz;etrozoL;Lelrozol;Lerozole;Laiquzuo
CBNumber
CB9286355
Molecular Formula
C17H11N5
Formula Weight
285.3
MOL File
112809-51-5.mol
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Letrozole Property

Melting point:
181-183°C
Boiling point:
563.5±60.0 °C(Predicted)
Density 
1.21±0.1 g/cm3(Predicted)
storage temp. 
2-8°C
solubility 
DMSO: >50mg/mL
form 
White powder
pka
1.52±0.11(Predicted)
color 
white to off-white
Merck 
14,5450
InChI
InChI=1S/C17H11N5/c18-9-13-1-5-15(6-2-13)17(22-12-20-11-21-22)16-7-3-14(10-19)4-8-16/h1-8,11-12,17H
InChIKey
HPJKCIUCZWXJDR-UHFFFAOYSA-N
SMILES
C(C1=CC=C(C=C1)C#N)(C1=CC=C(C=C1)C#N)N1C=NC=N1
CAS DataBase Reference
112809-51-5(CAS DataBase Reference)
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Safety

Hazard Codes 
Xi
Risk Statements 
36/37/38
Safety Statements 
26-36
WGK Germany 
3
RTECS 
DI4957000
HS Code 
2933997500
Hazardous Substances Data
112809-51-5(Hazardous Substances Data)
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Hazard and Precautionary Statements (GHS)

Symbol(GHS)
Signal word
Warning
Hazard statements

H373May cause damage to organs through prolonged or repeated exposure

Precautionary statements

P202Do not handle until all safety precautions have been read and understood.

P260Do not breathe dust/fume/gas/mist/vapours/spray.

P280Wear protective gloves/protective clothing/eye protection/face protection.

P308+P313IF exposed or concerned: Get medical advice/attention.

P405Store locked up.

P501Dispose of contents/container to..…

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N-Bromosuccinimide Price

Sigma-Aldrich
Product number
Y0000685
Product name
Letrozole
Purity
European Pharmacopoeia (EP) Reference Standard
Packaging
80 mg
Price
$156
Updated
2025/07/31
Sigma-Aldrich
Product number
1356971
Product name
Letrozole
Purity
United States Pharmacopeia (USP) Reference Standard
Packaging
200mg
Price
$425
Updated
2025/07/31
Sigma-Aldrich
Product number
182541
Product name
Aromatase Inhibitor II, Letrozole
Packaging
25mg
Price
$143
Updated
2022/05/15
TCI Chemical
Product number
L0248
Product name
Letrozole
Packaging
1G
Price
$185
Updated
2025/07/31
Cayman Chemical
Product number
11568
Product name
Letrozole
Purity
≥98%
Packaging
10mg
Price
$44
Updated
2024/03/01
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Letrozole Chemical Properties,Usage,Production

Indications and uses

Letrozole is part of a new generation of highly selective aromatase inhibitors and is an artificially synthesized benzotriazole derivative. Letrozole inhibits aromatase to lower estrogen levels, thus preventing estrogen from stimulating tumor growth. Its in vivo activity is 150-250 times stronger than that of first generation aromatase inhibitor Amarante. As it is highly selective, it will not impact glucocorticoid, mineralocorticoid and thyroid functions; even at high dosages, it will not have any inhibiting effects on adrenal corticosteroid secretion, giving it a high treatment index. Letrozole has no latent toxicity towards any bodily systems and target organs, has no mutagenicity and carcinogenic effects, has minimal toxic side effects, is well-tolerated, and has stronger anticancer effects than other aromatase inhibitors and antiestrogen drugs. Letrozole is suitable for advanced breast cancer postmenopausal patients who have not responded to estrogen-suppressing treatment and for early breast cancer treatment. It is used to treat postmenopausal patients with advanced breast cancer and serves as a second-line treatment to follow unsuccessful antiestrogen treatment. Compared to the current standard Tamoxifen treatment, Letrozole can better prevent the risk of breast cancer recurrence.

Pharmacokinetics

Absorption of oral letrozole is rapid and complete and steady state is achieved in 2–6 weeks with administration of letrozole 2.5mg once daily. The major route of elimination of letrozole is via metabolism to a pharmacologically inactive carbinol metabolite. The cytochrome P450 (CYP) 3A4 and CYP2A6 isozymes metabolize letrozole to a pharmacologically inactive carbinol metabolite. Renal excretion of a glucuronide conjugate of the carbinol metabolite of letrozole represents the major route of drug clearance.

Side effects

Randomized grouping studies have shown that daily oral ingestion of 2.5mg Letrozole leads to a 33% rate of drug-related negative reactions, a percentage much lower than AG group’s 46%. Negative reactions to Letrozole are mostly mild or moderate, consisting mostly of nausea (2-9%), headache (0-7%), bone pain (4-10%), hot flashes (0-9%) and weight gain (2-8%). Other uncommon side effects include constipation, diarrhea, itching, rash, joint pain, chest pain, abdominal pain, fatigue, insomnia, dizziness, edema, high blood pressure, arrhythmia, thrombosis, dyspnea, vaginal bleeding, etc.

Description

Letrozole, also known as Femara, is an orally active aromatase inhibitor that works by competitively inhibiting aromatase. This inhibition prevents the conversion of androgens to estrogen (estrogen stimulates breast tissues and breast cancer reoccurrence) and gonadal steroidogenesis. It can be used for the treatment of breast cancer that is hormonally-responsive or has an unknown receptor status in postmenopausal women. Besides this, Letrozole also has some off-label use such as ovarian stimulation, pretreatment of termination of pregnancy, treatment of gynecomastia, treatment of endometriosis, and promoting spermatogenesis for male patients of nonobstructive azoospermia.

Chemical Properties

white to light yellow crystal

Originator

Novartis (Switzerland)

History

Letrozole was discovered by scientists at the Swiss company Ciba-Geigy AG (now Novartis AG) In the 1980s while screening compounds for their ability to inhibit aromatase. Letrozole was far more potent than any other aromatase inhibitor discovered. As a result, its development was accelerated, leading to its approval in 1996 for the treatment of advanced breast cancer in France and other European countries. The following year letrozole was approved by the U.S. Food and Drug Administration. In addition to the drug’s general approval for the treatment of advanced breast cancer, in later years it was approved for multiple and specific applications. For example, in 2001 letrozole was approved in the United Kingdom specifically for the first-line treatment of advanced breast cancer, and in 2004 it was approved in the United States for what is known as extended adjuvant therapy.

Uses

A nonsteroidal aromatase inhibitor structurally related to Fadrozole. Antineoplastic

Uses

Letrozole has been used:

  • in organoid growth assay to determine its inhibitory capacity(48)
  • to investigate steroid receptor coactivator-1 (SRC-1) mediated endogenous estrogen regulation of hippocampal PSD-95(49)
  • to determine its effects on tumor-induced hyperalgesia(50)
  • for hormonal manipulation in rats(51)
  • to study its effects on lipocalin-2 (Lcn2)(52)
  • to determine its effects on mechanical hyperalgesia and aromatase expression(53)

Definition

ChEBI: Letrozole is a member of triazoles and a nitrile. It has a role as an antineoplastic agent and an EC 1.14.14.14 (aromatase) inhibitor.

Manufacturing Process

From 4-bromomethylbenzonitrile and 1H-[1,2,4]triazole was obtained 4- [1,2,4]triazol-1-ylmethylbenzonitrile. Treatment of that with strong base (tertBuOK) results in formation of the anion by removal of the relatively acidic benzyl proton. This anion was condensed with p-fluorobenzinitrile to give benzhydryl tetrazole (Letrozole)

brand name

Femara (Novar tis).

Therapeutic Function

Antineoplastic

General Description

Letrozole, 4,4'-(1H-1,2,4-triazol-1-ylmethylene)dibenzonitrile (Femara), is used for most of thesame indications as anastrozole. It reduces concentrations ofestrogens by 75% to 95%, with maximal suppressionachieved within 2 to 3 days. Letrozole is specific for aromataseinhibition, with no additional effects on adrenal corticoidbiosynthesis. CYPs 3A4 and 2A6 are involved in themetabolism of letrozole to the major carbinol metabolite,which is inactive. The loss of the triazole ring, which is involvedin coordination of the heme iron, would explain theloss of activity. Letrozole strongly inhibits CYP2A6 invitro, with moderate inhibition of CYP2C19. The effect ofthis in vitro inhibition on the pharmacokinetics of coadministereddrugs is unknown. Tamoxifen reduces the levels ofletrozole significantly if they are used together, so combinationtreatment with these agents is not recommended.

Biological Activity

Letrozole is a potent, cell-permeable inhibitor of aromatase (IC50 = 2 nM). It inhibits proliferation of estrogen receptor-positive (ER+) MCF-7 cells when used alone at concentrations ranging from 0.1 to 100 nM and when used at a concentration of 10 nM in combination with testosterone or 4-androstene-3,17-dione. It also reduces matrix metalloproteinase-2 (MMP-2) and MMP-9 levels in MCF-7 cells when used at a concentration of 10 nM. Letrozole (10 μg per day) reduces tumor growth in an MCF-7Ca ovariectomized-mouse xenograft model. Formulations containing letrozole have been used in the treatment of postmenopausal breast cancer.

Biochem/physiol Actions

Letrozole is a third generation nonsteroidal aromatase inhibitor. It is a competitive inhibitor of the aromatase enzyme system and thus inhibits the conversion of androgens to estrogens. 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.

Mechanism of action

Inhibition of arom atase by letrazole is competitive and highly specific , with no effect on enzymes that are responsible for the production of glucocorticosteroids and mineralocorticosteroids. This agent is significantly more effective than tamoxifen in treating horm one-dependent cancer.

Clinical Use

Femara was launched in France and the UK for second-line treatment of advanced breast cancer. Letrazole can be synthesized in two steps from 4- bromomethyl-benzonitrile with 1,2,4-triazole and is a third generation aromatase inhibitor. It is a highly specific inhibitor of P450arom which prevents the conversion of androstenedione to estrone. The reduction of plasma estrogen was immediate and long lasting. This is accomplished with no inhibition of other steroid biosynthesis making it the most selective aromatase inhibitor tested. Letrazole has remarkable antitumor activity, is well tolerated and has no toxic side effects. It is 10,000 times more potent than aminoglutethimide, in vivo, the first well established aromatase inhibitor.

storage

Store at +4°C

References

https://www.drugbank.ca/drugs/DB01006
https://en.wikipedia.org/wiki/Letrozole

Letrozole Preparation Products And Raw materials

Raw materials

Potassium tert-butoxide 4-fluorobenzonitrile 3-Amino-5-mercapto-1,2,4-triazole 4-Cyanobenzyl bromide

Preparation Products

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Letrozole Suppliers

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View Lastest Price from Letrozole manufacturers

Shanghai Yimeixin Technology Co., LTD
Product
Tamoxifen（Nolvadex） 112809-51-5
Price
US $0.00/Box
Min. Order
1Box
Purity
0.99
Supply Ability
0 tons
Release date
2025-09-26
Ningbo Qingteng Plastic Cost.,Ltd.
Product
Letrazole 112809-51-5
Price
US $10.00-7.00/VIAL
Min. Order
10VIAL
Purity
99.9
Supply Ability
20000
Release date
2025-07-25
Hebei Jiafan Trading Company Limited
Product
Letrazole 2.5mg 112809-51-5
Price
US $5.00/BOX
Min. Order
1BOX
Purity
99.99%
Supply Ability
100000000
Release date
2025-07-25

112809-51-5, LetrozoleRelated Search:

5-Methyl-1H-benzotriazole Chlorodimethylphenylsilane Tolyltriazole 1,2,4-Triazole 1H-Benzotriazole Ribavirin 1-CHLOROMETHYL-1H-1,2,4-TRIAZOLE 4-(1H-1,2,4-Triazol-1-ylmethyl)benzonitrile 4,4',4 -METHYLIDENETRISBENZONITRILE(IMPURITY OF LETROZOLE),4,4’,4”-Methyledenetrisbenzonitrile ( Impurity of Letrozole ) Ibandronate sodium monohydrate Irinotecan hydrochloride trihydrate LetrozoleN-Oxide 4,4'-(4H-1,2,4-TRIAZOL-4-YLMETHYLENE)BIS BENZONITRILE 4-((4-broMophenyl)(1H-1,2,4-triazol-1-yl)Methyl)benzonitrile (S)-1-(4-CYANOPHENYL)ETHANAMINE 4,4'-(1-METHYLENE) BIS-BENZONITRILE 5-Methyl-1,3-benzenediacetonitrile (R)-1-(4-CYANOPHENYL)ETHANAMINE

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