Formestane
Clinical data
Trade namesLentaron, others
Other names4-Hydroxyandrost-4-ene-3,17-dione
AHFS/Drugs.comInternational Drug Names
Routes of
administration		Intramuscular injection
Drug classAromatase inhibitor; Antiestrogen
ATC code
Identifiers
  • (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
PubChem CID
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.153.838 Edit this at Wikidata
Chemical and physical data
FormulaC19H26O3
Molar mass302.414 g·mol−1
3D model (JSmol)
  • 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=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 checkY
  • Key:OSVMTWJCGUFAOD-KZQROQTASA-N checkY
 ☒NcheckY (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 cancer in postmenopausal 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was not approved by the United States FDA and the injectable form that was used in Europe in the past has been withdrawn from the market.[2] Formestane is an analogue of androstenedione.

Formestane is often used to suppress the production of estrogens from anabolic steroids or prohormones. 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.

Pharmacodynamics of aromatase inhibitors
Generation Medication Dosage % inhibitiona Classb IC50c
First Testolactone 250 mg 4x/day p.o. ? Type I ?
100 mg 3x/week i.m. ?
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
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%
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

  1. ^ 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.
  2. ^ "Formestane".


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