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
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was not approved by the United States FDA and the injectable form that was used in Europe in the past has been withdrawn from the market.[2] Formestane is an analogue of androstenedione.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
GenerationMedicationDosage % inhibitionaClassbIC50c
FirstTestolactone250 mg 4x/day p.o. ?Type I ?
100 mg 3x/week i.m. ?
Rogletimide200 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 ?
Aminoglutethimide250 mg mg 4x/day p.o.90.6%Type II4,500 nM
SecondFormestane125 mg 1x/day p.o.
125 mg 2x/day p.o.
250 mg 1x/day p.o.
72.3%
70.0%
57.3%
Type I30 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%
Fadrozole1 mg 1x/day p.o.
2 mg 2x/day p.o.
82.4%
92.6%
Type II ?
ThirdExemestane25 mg 1x/day p.o.97.9%Type I15 nM
Anastrozole1 mg 1x/day p.o.
10 mg 1x/day p.o.
96.7–97.3%
98.1%
Type II10 nM
Letrozole0.5 mg 1x/day p.o.
2.5 mg 1x/day p.o.
98.4%
98.9%–>99.1%
Type II2.5 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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