|Systematic (IUPAC) name|
|Biological half-life||24 hours|
|CAS Registry Number|
|Molecular mass||389.33 g/mol|
|Melting point||70 to 74 °C (158 to 165 °F)|
|(what is this?)|
Enobosarm ((2S)-3-(4-cyanophenoxy)-N-[4-cyano-3-(trifluoromethyl)phenyl]-2-hydroxy-2-methylpropanamide) (also known as ostarine, GTx-024, and MK-2866) is an investigational selective androgen receptor modulator (SARM) from GTX, Inc for treatment of conditions such as muscle wasting and osteoporosis, formerly under development by Merck & Company.
According to a recent paper authored by GTx, "Readers are cautioned to note that the name ostarine is often mistakenly linked to the chemical structure of [S-4], which is also known as andarine. The chemical structure of ostarine has not been publicly disclosed." While GTx has not formally disclosed the structure of ostarine, the chemical composition of ostarine is revealed in patent databases such the WIPO and discussed by Zhang et al., 2009 in the primary literature. Various SARM chemotypes exist (aryl propionamides, quinolines, quinolinones, bicyclic hydantoins), though aryl propionamides such as ostarine, andarine/S-4, and S-23 represent some of the most advanced putative therapeutics under investigation. In terms of atom connectivity, enobosarm differs from andarine by cyano substitutions on the phenyl rings as it replaces both the nitro and acetamido moieties.
Selective androgen receptor modulators may be used by athletes to assist in training and increase physical stamina and fitness, potentially producing effects similar to anabolic steroids. For this reason, SARMs were banned by the World Anti-Doping Agency in January 2008 despite no drugs from this class yet being in clinical use, and blood tests for all known SARMs have been developed.
In June 2015 Azerbaijan's Chaltu Beji has tested positive for doping at the 2015 European Games in Baku. The 18-year-old Ethiopian-born Beji tested positive for the banned substance ostarine in a urine sample with a B sample confirming the result. She won the 3,000 meter steeplechase event despite falling at the last water jump, she was disqualified because of the positive tests. 
- James T. Dalton, Duane D. Miller, Donghua Yin, Yali He. Selective androgen receptor modulators and methods of use thereof. US Patent 6569896
- Mohler ML, Bohl CE, Jones A et al. (June 2009). "Nonsteroidal selective androgen receptor modulators (SARMs): dissociating the anabolic and androgenic activities of the androgen receptor for therapeutic benefit". J. Med. Chem. 52 (12): 3597–617. doi:10.1021/jm900280m. PMID 19432422.
- WO application 2008127717, James T. Dalton and Duane D. Miller, "Selective Androgen Receptor Modulators for Treating Diabetes", published Oct 23, 2008, assigned to University of Tennessee Research Foundation, James T. Dalton, and Duane D. Miller
- Zhang X, Lanter JC, Sui Z (September 2009). "Recent advances in the development of selective androgen receptor modulators". Expert Opin Ther Pat 19 (9): 1239–58. doi:10.1517/13543770902994397. PMID 19505196.
- Jones A, Chen J, Hwang DJ, Miller DD, Dalton JT (January 2009). "Preclinical characterization of a (S)-N-(4-cyano-3-trifluoromethyl-phenyl)-3-(3-fluoro, 4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide: a selective androgen receptor modulator for hormonal male contraception". Endocrinology 150 (1): 385–95. doi:10.1210/en.2008-0674. PMC 2630904. PMID 18772237.
- Thevis M, Kohler M, Schlörer N, Kamber M, Kühn A, Linscheid MW, Schänzer W. Mass spectrometry of hydantoin-derived selective androgen receptor modulators. Journal of Mass Spectrometry. 2008 May;43(5):639-50. PMID 18095383
- Thevis M, Kohler M, Thomas A, Maurer J, Schlörer N, Kamber M, Schänzer W. Determination of benzimidazole- and bicyclic hydantoin-derived selective androgen receptor antagonists and agonists in human urine using LC-MS/MS. Analytical and Bioanalytical Chemistry. 2008 May;391(1):251-61. PMID 18270691