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Formestane

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Formestane
Clinical data

Trade names	Lentaron, others
Other names	4-Hydroxyandrost-4-ene-3,17-dione
AHFS/Drugs.com	International Drug Names
Routes of administration	Intramuscular injection
Drug class	Aromatase inhibitor; Antiestrogen
ATC code	L02BG02 (WHO)
Identifiers
IUPAC name (8R,9S,10R,13S,14S)-4-hydroxy-10,13-dimethyl-2,6,7,8,9,11,12,14,15,16-decahydro-1H-cyclopenta[a]phenanthrene-3,17-dione
CAS Number	566-48-3^Y
PubChem CID	11273
ChemSpider	10799^Y
UNII	PUB9T8T355
KEGG	D07260^Y
ChEBI	CHEBI:75172^N
ChEMBL	ChEMBL132530^Y
CompTox Dashboard (EPA)	DTXSID3034113
ECHA InfoCard	100.153.838
Chemical and physical data
Formula	C₁₉H₂₆O₃
Molar mass	302.414 g·mol⁻¹
3D model (JSmol)	Interactive image
SMILES O=C4C(/O)=C3/CC[C@@H]2[C@H](CC[C@@]1(C(=O)CC[C@H]12)C)[C@@]3(C)CC4
InChI 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^Y Key:OSVMTWJCGUFAOD-KZQROQTASA-N^Y
^NY (what is this?) (verify)

Formestane, formerly sold under the brand name Lentaron among others, is a steroidal, selective aromatase inhibitor which is used in the treatment of estrogen receptor-positive breast cancerinpostmenopausal women.^[1] The drug is not active orally, and was available only as an intramuscular depot injection. Formestane was not approved by the United States FDA and the injectable form that was used in Europe in the past has been withdrawn from the market.^[2] Formestane is an analogueofandrostenedione.

Formestane is often used to suppress the production of estrogens from anabolic steroidsorprohormones. It also acts as a prohormone to 4-hydroxytestosterone, an active steroid which displays weak androgenic activity in addition to acting as a weak aromatase inhibitor.

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Pharmacodynamics of aromatase inhibitors
Generation	Medication	Dosage	% inhibition^a	Class^b	IC₅₀^c
First	Testolactone	250 mg 4x/day p.o.	?	Type I	?
	Testolactone	100 mg 3x/week i.m.	?	Type I	?
	Rogletimide	200 mg 2x/day p.o. 400 mg 2x/day p.o. 800 mg 2x/day p.o.	50.6% 63.5% 73.8%	Type II	?
	Aminoglutethimide	250 mg mg 4x/day p.o.	90.6%	Type II	4,500 nM
Second	Formestane	125 mg 1x/day p.o. 125 mg 2x/day p.o. 250 mg 1x/day p.o.	72.3% 70.0% 57.3%	Type I	30 nM
	Formestane	250 mg 1x/2 weeks i.m. 500 mg 1x/2 weeks i.m. 500 mg 1x/1 week i.m.	84.8% 91.9% 92.5%	Type I	30 nM
	Fadrozole	1 mg 1x/day p.o. 2 mg 2x/day p.o.	82.4% 92.6%	Type II	?
Third	Exemestane	25 mg 1x/day p.o.	97.9%	Type I	15 nM
	Anastrozole	1 mg 1x/day p.o. 10 mg 1x/day p.o.	96.7–97.3% 98.1%	Type II	10 nM
	Letrozole	0.5 mg 1x/day p.o. 2.5 mg 1x/day p.o.	98.4% 98.9%–>99.1%	Type II	2.5 nM
Footnotes: ^a = In postmenopausal women. ^b = Type I: Steroidal, irreversible (substrate-binding site). Type II: Nonsteroidal, reversible (binding to and interference with the cytochrome P450 heme moiety). ^c = In breast cancer homogenates. Sources: See template.

References[edit]

^ Pérez Carrión R, Alberola Candel V, Calabresi F, et al. (1994). "Comparison of the selective aromatase inhibitor formestane with tamoxifen as first-line hormonal therapy in postmenopausal women with advanced breast cancer". Ann. Oncol. 5 (Suppl 7): S19–24. PMID 7873457.

^ "Formestane".

Estrogens and antiestrogens

Estrogens

ER agonists

Steroidal: Alfatradiol
Certain androgens/anabolic steroids (e.g., testosterone, testosterone esters, methyltestosterone, metandienone, nandrolone esters) (via estrogenic metabolites)
Certain progestins (e.g., norethisterone, noretynodrel, etynodiol diacetate, tibolone)
Clomestrone
Cloxestradiol acetate
Conjugated estriol
Conjugated estrogens
Epiestriol
Epimestrol
Esterified estrogens
Estetrol^†
Estradiol
Estradiol esters (e.g., estradiol acetate, estradiol benzoate, estradiol cypionate, estradiol enanthate, estradiol undecylate, estradiol valerate, polyestradiol phosphate, estradiol ester mixtures (Climacteron))
Estramustine phosphate
Estriol
Estriol esters (e.g., estriol succinate, polyestriol phosphate)
Estrogenic substances
Estrone
Estrone esters
- Estrone sulfate
- Estropipate (piperazine estrone sulfate)
Ethinylestradiol^#
- Ethinylestradiol sulfonate
Hydroxyestrone diacetate
Mestranol
Methylestradiol
Moxestrol
Nilestriol
Prasterone (dehydroepiandrosterone; DHEA)
- Prasterone enanthate
- Prasterone sulfate
Promestriene
Quinestradol
Quinestrol

Progonadotropins

Antiandrogens (e.g., bicalutamide)
GnRH agonists (e.g., GnRH (gonadorelin), leuprorelin)
Gonadotropins (e.g., FSHTooltip follicle-stimulating hormone, LHTooltip luteinizing hormone)

Antiestrogens

ERTooltip Estrogen receptor antagonists (incl. SERMsTooltip selective estrogen receptor modulators/SERDsTooltip selective estrogen receptor downregulators)	Acolbifene^† Anordrin Bazedoxifene Broparestrol Clomifene^# Cyclofenil Enclomifene^† Epitiostanol Lasofoxifene Mepitiostane Ormeloxifene Ospemifene Raloxifene Tamoxifen^# Toremifene Exclusively antagonistic: Elacestrant Fulvestrant Noncompetitive inhibitors: Trilostane
Aromatase inhibitors	First-generation: Aminoglutethimide Testolactone Second-generation: Fadrozole Formestane Third-generation: Anastrozole Exemestane Letrozole
Antigonadotropins	Androgens/anabolic steroids (e.g., testosterone, testosterone esters, nandrolone esters, oxandrolone, fluoxymesterone) D₂ receptor antagonists (prolactin releasers) (e.g., domperidone, metoclopramide, risperidone, haloperidol, chlorpromazine, sulpiride) GnRH agonists (e.g., leuprorelin, goserelin) GnRH antagonists (e.g., cetrorelix, elagolix) Progestogens (e.g., chlormadinone acetate, cyproterone acetate, gestonorone caproate, hydroxyprogesterone caproate, medroxyprogesterone acetate, megestrol acetate)
Others	Mixed mechanism of action: Danazol Gestrinone Androstenedione immunogens: Androvax (androstenedione albumin) Ovandrotone albumin (Fecundin)