FORMESTANE

Details

Stereochemistry	ABSOLUTE
Molecular Formula	C19H26O3
Molecular Weight	302.4079
Optical Activity	UNSPECIFIED
Defined Stereocenters	5 / 5
E/Z Centers	0
Charge	0

SHOW SMILES / InChI

Structure Search

SMILES

C[C@]12CC[C@H]3[C@@H](CCC4=C(O)C(=O)CC[C@]34C)[C@@H]1CCC2=O

InChI

InChIKey=OSVMTWJCGUFAOD-KZQROQTASA-N

InChI=1S/C19H26O3/c1-18-10-8-15(20)17(22)14(18)4-3-11-12-5-6-16(21)19(12,2)9-7-13(11)18/h11-13,22H,3-10H2,1-2H3/t11-,12-,13-,18+,19-/m0/s1

HIDE SMILES / InChI

Molecular Formula	C19H26O3
Molecular Weight	302.4079
Charge	0
Count

Stereochemistry	ABSOLUTE
Additional Stereochemistry	No
Defined Stereocenters	5 / 5
E/Z Centers	0
Optical Activity	UNSPECIFIED

Description
Sources: https://anabolic.org/formestane-lentaron/
Curator's Comment: description was created based on several sources, including https://www.drugs.com/international/formestane.html | https://www.ncbi.nlm.nih.gov/pubmed/15183852 | https://www.drugbank.ca/drugs/DB08905

Formestane (trade name Lentaron) is a type I, steroidal, selective aromatase inhibitor used in the treatment of estrogen receptor-positive breast cancer in postmenopausal women. Formestane has poor oral bioavailability and thus must be administered fortnightly (bi-weekly) by intramuscular injection. Formestane is a second generation, irreversible, steroidal aromatase inhibitor. It inhibits the aromatase enzyme responsible for converting androgens to estrogens, thereby preventing estrogen production. Estrogen-sensitive breast cancer cells depend on estrogen for viability. Thus removal of estrogen from the body can be an effective treatment for hormone-sensitive breast cancers. Common side effects associated with the use of an aromatase inhibitor include hot flashes, joint pain, weakness, fatigue, mood changes, depression, high blood pressure, swelling of the arms/legs, and headache. Aromatase inhibitors may also decrease bone mineral density, which may lead to osteoporosis and an increase in fractures in susceptible patients. Formestane was the first selective aromatase inhibitor to be developed as a prescription drug, first appearing in Europe during the mid-1990s under the Lentaron Depot brand name. With the emergence of newer and more effective aromatase inhibitors, however, formestane soon lost market presence at a rapid rate. Most of the initial Lentaron preparations have since been discontinued. Currently, formestane (categorized as an anti-estrogenic agent) is prohibited from use in sports in accordance with the regulations of the World Anti-Doping Agency. The drug remains available today, but only in a small number of nations. This includes Austria, Brazil, Czech Republic, Hong Kong, and Turkey.

Originator

Approval Year

Targets

Primary Target	Pharmacology	Condition	Potency
3-keto-steroid reductase 1 Target ID: CHEMBL5999 Sources: https://www.ncbi.nlm.nih.gov/pubmed/19772289	Inhibitor 8504
Cytochrome P450 19A1 39 Target ID: CHEMBL1978 Sources: https://www.ncbi.nlm.nih.gov/pubmed/20926163	Inhibitor 8504		42.0 nM [IC50]

Conditions

Condition	Modality	Targets	Highest Phase	Product
Advanced breast cancer 6 Sources: https://www.ncbi.nlm.nih.gov/pubmed/15183852	Primary		Approved 8583	Lentaron Approved Use Unknown

C_max

Value	Dose	Analyte	Population
48 nM CLINICAL TRIAL https://pubmed.ncbi.nlm.nih.gov/11358673/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:	FORMESTANE plasma	Homo sapiens population: UNHEALTHY age: ADULT sex: FEMALE food status: UNKNOWN
22 ng/mL EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/9831486/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:	FORMESTANE plasma	Homo sapiens population: HEALTHY age: ADULT sex: MALE food status: UNKNOWN
13.5 ng/mL EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/9831486/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:	FORMESTANE plasma	Homo sapiens population: HEALTHY age: ADULT sex: MALE food status: UNKNOWN

AUC

Value	Dose	Analyte	Population
5055 nM × h CLINICAL TRIAL https://pubmed.ncbi.nlm.nih.gov/11358673/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:	FORMESTANE plasma	Homo sapiens population: UNHEALTHY age: ADULT sex: FEMALE food status: UNKNOWN
1135.2 ng × h/mL EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/9831486/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:	FORMESTANE plasma	Homo sapiens population: HEALTHY age: ADULT sex: MALE food status: UNKNOWN
978.3 ng × h/mL EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/9831486/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:	FORMESTANE plasma	Homo sapiens population: HEALTHY age: ADULT sex: MALE food status: UNKNOWN

T_1/2

Value	Dose	Co-administered	Analyte	Population
57.33 h EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/9831486/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:		FORMESTANE plasma	Homo sapiens population: HEALTHY age: ADULT sex: MALE food status: UNKNOWN
85.66 h EXPERIMENT https://pubmed.ncbi.nlm.nih.gov/9831486/	250 mg single, intramuscular dose: 250 mg route of administration: Intramuscular experiment type: SINGLE co-administered:		FORMESTANE plasma	Homo sapiens population: HEALTHY age: ADULT sex: MALE food status: UNKNOWN

F_unbound

Value	Dose	Co-administered	Analyte	Population
16% REVIEW https://pubmed.ncbi.nlm.nih.gov/7680986/			FORMESTANE plasma	Homo sapiens

Doses

Dose	Population	Adverse events
250 mg 1 times / 2 weeks multiple, intramuscular Studied dose Dose: 250 mg, 1 times / 2 weeks Route: intramuscular Route: multiple Dose: 250 mg, 1 times / 2 weeks Sources: https://pubmed.ncbi.nlm.nih.gov/15183852/	unhealthy, ADULT Health Status: unhealthy Age Group: ADULT Sex: F Food Status: UNKNOWN Sources: https://pubmed.ncbi.nlm.nih.gov/15183852/	Sources: https://pubmed.ncbi.nlm.nih.gov/15183852/
500 mg 1 times / week multiple, intramuscular Studied dose Dose: 500 mg, 1 times / week Route: intramuscular Route: multiple Dose: 500 mg, 1 times / week Sources: https://pubmed.ncbi.nlm.nih.gov/2201397/	unhealthy, ADULT Health Status: unhealthy Age Group: ADULT Sex: M Food Status: UNKNOWN Sources: https://pubmed.ncbi.nlm.nih.gov/2201397/	Disc. AE: Injection site pain... AEs leading to discontinuation/dose reduction: Injection site pain (10.5%) Sources: https://pubmed.ncbi.nlm.nih.gov/2201397/

AEs

AE	Significance	Dose	Population
Injection site pain	10.5% Disc. AE	500 mg 1 times / week multiple, intramuscular Studied dose Dose: 500 mg, 1 times / week Route: intramuscular Route: multiple Dose: 500 mg, 1 times / week Sources: https://pubmed.ncbi.nlm.nih.gov/2201397/	unhealthy, ADULT Health Status: unhealthy Age Group: ADULT Sex: M Food Status: UNKNOWN Sources: https://pubmed.ncbi.nlm.nih.gov/2201397/

Overview

CYP3A4	CYP2C9	CYP2D6	hERG
inducer 1087 inhibitor 2252	inhibitor 2438	inhibitor 2507	inhibitor 2217

OverviewOther

Other Inhibitor	Other Substrate	Other Inducer
OATP1B3 961 OATP1B1 1079 CYP2C19 2057 BCRP 910 CYP1A2 2153 P-gp 1741 CYP19A1 429	P-gp 2052

Drug as perpetrator

Target	Modality	Activity
CYP2C19 2141	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 20.0	inconclusive [IC50 17.3768 uM]
CYP2C9 2497	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 25.0	inconclusive [IC50 21.8761 uM]
CYP2D6 2546	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 31.0	inconclusive [IC50 30.9008 uM]
CYP1A2 2333	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 40.0	inconclusive [IC50 56.3813 uM]
BCRP 985	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 83.0	no
CYP3A4 2633	inducer 1966 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 339.0	no
MRP1 232	activator 342 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 69.0	no
P-gp 1932	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 84.0	no
CYP19A1 430	inhibitor 4027 Sources: https://pubmed.ncbi.nlm.nih.gov/27160054/	yes [IC50 0.042 uM]
CYP3A4 2633	inhibitor 4027 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 10.0	yes [IC50 2.1876 uM]
OATP1B1 1095	inhibitor 4027 Sources: https://www.ebi.ac.uk/chembl/g/#browse/activities/full_state/eyJsaXN0Ijp7InNldHRpbmdzX3BhdGgiOiJFU19JTkRFWEVTX05PX01BSU5fU0VBUkNILkFDVElWSVRZIiwiY3VzdG9tX3F1ZXJ5IjoidGFyZ2V0X2NoZW1ibF9pZDpDSEVNQkwxNjk3NjY4IiwidXNlX2N1c3RvbV9xdWVyeSI6dHJ1ZSwic2VhcmNoX3Rlcm0iOiIiLCJ0ZXh0X2ZpbHRlciI6IkNIRU1CTDEzMjUzMCJ9fQ==	yes [Inhibition 10 uM]
OATP1B3 970	inhibitor 4027 Sources: https://www.ebi.ac.uk/chembl/g/#browse/activities/full_state/eyJsaXN0Ijp7InNldHRpbmdzX3BhdGgiOiJFU19JTkRFWEVTX05PX01BSU5fU0VBUkNILkFDVElWSVRZIiwiY3VzdG9tX3F1ZXJ5IjoidGFyZ2V0X2NoZW1ibF9pZDpDSEVNQkwxNzQzMTIxIiwidXNlX2N1c3RvbV9xdWVyeSI6dHJ1ZSwic2VhcmNoX3Rlcm0iOiIiLCJ0ZXh0X2ZpbHRlciI6IkNIRU1CTDEzMjUzMCJ9fQ==	yes [Inhibition 10 uM]

Drug as victim

Target	Modality	Activity	Metabolite	Clinical evidence
P-gp 2052	substrate 4014 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 335 \| 337	no

Tox targets

Target	Modality	Activity	Metabolite	Clinical evidence
hERG 2263	inhibitor 2237 Sources: https://pubchem.ncbi.nlm.nih.gov/compound/11273#section=Biological-Test-Results Page: 377.0

PubMed

Title	Date	PubMed
A comparison of two human cell lines and two rat gonadal cell primary cultures as in vitro screening tools for aromatase modulation.	2012-02	22120136
Testosterone, not 5α-dihydrotestosterone, stimulates LRH-1 leading to FSH-independent expression of Cyp19 and P450scc in granulosa cells.	2011-04	21273442
Design, synthesis, and biological evaluation of imidazolyl derivatives of 4,7-disubstituted coumarins as aromatase inhibitors selective over 17-α-hydroxylase/C17-20 lyase.	2011-03-24	21341743
Understanding the effects of atrazine on steroidogenesis in rat granulosa and H295R adrenal cortical carcinoma cells.	2011-02	21126571
Effects of adlay (Coix lachryma-jobi L. var. ma-yuen Stapf.) hull extracts on the secretion of progesterone and estradiol in vivo and in vitro.	2007-10	17895526
Modulation of aromatase activity and mRNA by various selected pesticides in the human choriocarcinoma JEG-3 cell line.	2006-11-10	16996190
Inhibition of rainbow trout (Oncorhynchus mykiss) P450 aromatase activities in brain and ovarian microsomes by various environmental substances.	2006-11	17081805
Inhibition and induction of aromatase (CYP19) activity by brominated flame retardants in H295R human adrenocortical carcinoma cells.	2005-12	16177243
New insights into the mechanism of imposex induction in the dogwhelk Nucella lapillus.	2005-05	15964245
Mammalian lignans and genistein decrease the activities of aromatase and 17beta-hydroxysteroid dehydrogenase in MCF-7 cells.	2005-04	15876411
Induction and inhibition of aromatase (CYP19) activity by natural and synthetic flavonoid compounds in H295R human adrenocortical carcinoma cells.	2004-11	15319488
Methadone metabolism by human placenta.	2004-08-01	15242824
Expression and mitogenic effect of fibroblast growth factor-9 in human endometriotic implant is regulated by aberrant production of estrogen.	2003-11	14602803
Screening of selected pesticides for inhibition of CYP19 aromatase activity in vitro.	2000-06	10806373
2-Chloro-s-triazine herbicides induce aromatase (CYP19) activity in H295R human adrenocortical carcinoma cells: a novel mechanism for estrogenicity?	2000-03	10746939
Comparison of the selective aromatase inhibitor formestane with tamoxifen as first-line hormonal therapy in postmenopausal women with advanced breast cancer.	1994	7873457

Patents

Sample Use Guides

In Vivo Use Guide

250 mg i.m. fortnightly

Route of Administration: Intramuscular

In Vitro Use Guide

Antiproliferative activity of selected androstane derivatives was evaluated by tetrazolium colorimetric MTT assay, in microwell plates, after exposure of the cells to the tested compounds at five different concentrations ranging tenfold from 0.01 to 100 mkM. Activity against both types of breast cancer cell lines, MCF-7 and MDA-MB-231 was tested during three incubation periods (24, 48 and 72 h). Reference compounds used in this assay were Doxorubicin (Dox) as a nonselective anticancer drug, and formestane (For) as mechanism-based aromatase inactivator

Substance Class	Chemical Created by `admin` on `Wed Apr 02 07:55:35 GMT 2025` Edited by `admin` on `Wed Apr 02 07:55:35 GMT 2025`
Record UNII	PUB9T8T355
Record Status	`Validated (UNII)`
Record Version

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Name

Type

Language

FORMESTANE

Official Name

English

LENTARON

Preferred Name

English

4-HYDROXYANDROST-4-ENE-3,17-DIONE

Systematic Name

English

Formestane [WHO-DD]

Common Name

English

NSC-282175

Code

English

4-OH-ANDROSTENE-3,17-DIONE

Common Name

English

FORMESTANE [MART.]

Common Name

English

formestane [INN]

Common Name

English

FORMESTANE [MI]

Common Name

English

4-hydroxy-androst-4-ene-3,17-dione

Systematic Name

English

CGP-32349

Code

English

CGP 32349

Code

English

Classification Tree Code System Code

WHO-VATC

QL02BG02