WARNING: This product is for research use only, not for human or veterinary use.

MedKoo CAT#: 100376

CAS#: 566-48-3

Description: Formestane is a synthetic steroidal substance with antineoplastic activity. Formestane binds irreversibly to and inhibits the enzyme aromatase, thereby blocking the conversion of cholesterol to pregnenolone and the peripheral aromatization of androgenic precursors into estrogens.

Chemical Structure

CAS# 566-48-3

Theoretical Analysis

MedKoo Cat#: 100376
Name: Formestane
CAS#: 566-48-3
Chemical Formula: C19H26O3
Exact Mass: 302.18819
Molecular Weight: 302.41
Elemental Analysis: C, 75.46; H, 8.67; O, 15.87

Price and Availability

Size Price Availability Quantity
1.0g USD 150.0 Same day
2.0g USD 250.0 Same day
5.0g USD 550.0 Same day
10.0g USD 1050.0 Same day
20.0g USD 1650.0 Same day
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Synonym: CGP32349; CGP 32349; CGP-32349; 4OHA; 4OHAD; Formestane; Lentaron.

IUPAC/Chemical Name: (8R,9S,10R,13S,14S)-4-hydroxy-10,13-dimethyl-7,8,9,10,11,12,13,14,15,16-decahydro-1H-cyclopenta[a]phenanthrene-3,17(2H,6H)-dione


InChi Code: 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

SMILES Code: O=C(C(O)=C1CC[C@@]2([H])[C@]3([H])CC4)CC[C@]1(C)[C@@]2([H])CC[C@]3(C)C4=O

Appearance: Solid powder

Purity: >98% (or refer to the Certificate of Analysis)

Shipping Condition: Shipped under ambient temperature as non-hazardous chemical. This product is stable enough for a few weeks during ordinary shipping and time spent in Customs.

Storage Condition: Dry, dark and at 0 - 4 C for short term (days to weeks) or -20 C for long term (months to years).

Solubility: Soluble in DMSO, not in water

Shelf Life: >5 years if stored properly

Drug Formulation: This drug may be formulated in DMSO

Stock Solution Storage: 0 - 4 C for short term (days to weeks), or -20 C for long term (months).

HS Tariff Code: 2934.99.9001

Preparing Stock Solutions

The following data is based on the product molecular weight 302.41 Batch specific molecular weights may vary from batch to batch due to the degree of hydration, which will affect the solvent volumes required to prepare stock solutions.

Recalculate based on batch purity %
Concentration / Solvent Volume / Mass 1 mg 5 mg 10 mg
1 mM 1.15 mL 5.76 mL 11.51 mL
5 mM 0.23 mL 1.15 mL 2.3 mL
10 mM 0.12 mL 0.58 mL 1.15 mL
50 mM 0.02 mL 0.12 mL 0.23 mL

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1: Martin GD, Narvaez J, Marti A. Synthesis and bioconversions of formestane. J Nat Prod. 2013 Oct 25;76(10):1966-9. doi: 10.1021/np400585t. Epub 2013 Sep 27. PubMed PMID: 24074257.

2: Polet M, Van Renterghem P, Van Gansbeke W, Van Eenoo P. Profiling of urinary formestane and confirmation by isotope ratio mass spectrometry. Steroids. 2013 Nov;78(11):1103-9. doi: 10.1016/j.steroids.2013.07.011. Epub 2013 Aug 7. PubMed PMID: 23933120.

3: Leung GN, Kwok WH, Wan TS, Lam KK, Schiff PJ. Metabolic studies of formestane in horses. Drug Test Anal. 2013 Jun;5(6):412-9. doi: 10.1002/dta.1444. Epub 2013 Jan 21. PubMed PMID: 23339113.

4: Piper T, Fusshöller G, Emery C, Schänzer W, Saugy M. Investigations on carbon isotope ratios and concentrations of urinary formestane. Drug Test Anal. 2012 Dec;4(12):942-50. doi: 10.1002/dta.386. Epub 2012 Feb 22. PubMed PMID: 22354842.

5: Cavaliere C, Corvigno S, Galgani M, Limite G, Nardone A, Veneziani BM. Combined inhibitory effect of formestane and herceptin on a subpopulation of CD44+/CD24low breast cancer cells. Cancer Sci. 2010 Jul;101(7):1661-9. doi: 10.1111/j.1349-7006.2010.01593.x. Epub 2010 Apr 19. PubMed PMID: 20491779.

6: Sharma SK, Zheng W, Joshua AV, Abrams DN, McEwan AJ. Synthesis and evaluation of novel 4-amino-4,6-androstadiene-3,17-dione: an analog of formestane. Bioorg Med Chem Lett. 2008 Oct 15;18(20):5563-6. doi: 10.1016/j.bmcl.2008.09.018. Epub 2008 Sep 22. PubMed PMID: 18815032.

7: Nisslein T, Freudenstein J. Coadministration of the aromatase inhibitor formestane and an isopropanolic extract of black cohosh in a rat model of chemically induced mammary carcinoma. Planta Med. 2007 Apr;73(4):318-22. Epub 2007 Mar 12. PubMed PMID: 17354167.

8: Czerny B, Teister M, Juzyszyn Z, Modrzejewski A, Pawlik A. Effect of 4-hydroxyandrost-4-ene-3,17-dione (formestane) on the bile secretion and metabolism of 4-(14)C-cholesterol to bile acids. Pharmacol Rep. 2005 Nov-Dec;57(6):896-900. PubMed PMID: 16382215.

9: Zilembo N, Bajetta E, Bichisao E, Martinetti A, La Torre I, Bidoli P, Longarini R, Portale T, Seregni E, Bombardieri E. The estrogen suppression after sequential treatment with formestane in advanced breast cancer patients. Biomed Pharmacother. 2004 May;58(4):255-9. PubMed PMID: 15183852.

10: Freue M, Kjaer M, Boni C, Joliver J, Jänicke F, Willemse PH, Coombes RC, Van Belle S, Pérez-Carrión R, Zieschang J, Ibarra de Palacios P, Rose C. Open comparative trial of formestane versus megestrol acetate in postmenopausal patients with advanced breast cancer previously treated with tamoxifen. Breast. 2000 Feb;9(1):9-16. PubMed PMID: 14731578.

Additional Information

Formestane belongs to a class of drugs known as 2 aromatase inhibitors. It is used in the treatment of estrogen-receptor positive breast cancer in post-menopausal women. It is available as an intramuscular depot injection (Lentaron). Formestane is often used to suppress estrogen production 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 mild aromatase inhibitor. Formestane has poor oral bioavailability and as such is no longer popular as many orally available aromatase inhibitors have been developed. see