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Clinical data
Routes of
By mouth
ATC code
  • none
Legal status
Legal status
Pharmacokinetic data
Biological half-life 24 hours[citation needed]
Synonyms Ostarine; S-22; GTx-024;[1] MK-2866
CAS Number
PubChem CID
Chemical and physical data
Formula C19H14F3N3O3
Molar mass 389.33 g/mol
3D model (JSmol)
Melting point 70 to 74 °C (158 to 165 °F)

Enobosarm, also known as ostarine, 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.[2]


Ostarine versus andarine

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."[3] While GTx has not formally disclosed the structure of ostarine, the chemical composition of ostarine is revealed in patent databases such the WIPO[4] and discussed by Zhang et al., 2009 in the primary literature.[5] 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.[6] 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.[7][8]

In June 2013, professional cyclist Nikita Novikov was provisionally suspended after a possible breach of anti-doping rules, due to a positive A-sample result for Ostarine.[9]

UFC Fighter Tim Means was pulled from a fight in February 2017 after testing positive for Ostarine in a pre-fight drug screening administered by USADA.[10]

In June 2015 Azerbaijan's Chaltu Beji 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.[11]

In May 2016, Romanian-Canadian professional boxer Lucian Bute, former super middleweight world titleholder, tested positive for Ostarine after his draw against Swedish professional boxer and titleholder Badou Jack on April 30 at the D.C. Armory in Washington, D.C.[12]

On December 16, 2016, Russian heavyweight boxer Alexandre Povetkin tested positive for Ostarine less than a day before an interim WBC title fight against former WBC champ Bermane Stiverne. The fight, which was scheduled for December 17 in Yekaterinburg, Russia, was cancelled.[13]

In March 2016, Australian triathlete Lisa Marangon received a 4-year ban ending in March 2020 for use of banned substance Ostarine. American triathlete Ashley Paulson was given a 6-month suspension for use of banned substance Ostarine because officials accepted her contention that the banned drug positive came from a contaminated supplement.[14]

In February 2017, American triathlete Beth Gerdes was given a 2-year suspension for presence of ostarine, and American triathlete Lauren Barnett was given a 6-month suspension for the presence of Ostarine. Both triathletes claimed contamination from salt tablet supplements. Lauren Barnett was able to provide tablets and sealed bottle tablets which both tested positive for contamination, thus only the 6-month suspension. The 2-year suspension still stands for Beth Gerdes who provided tablets for testing, but tests showed only low levels of ostarine not high enough to confirm the finding. .[15]

In February 2017, UFC light heavyweight Tom Lawlor was suspended for two years following a positive test for ostarine.[16]

See also[edit]


  1. ^ Srinath R, Dobs A (2014). "Enobosarm (GTx-024, S-22): a potential treatment for cachexia". Future Oncol. 10 (2): 187–94. PMID 24490605. doi:10.2217/fon.13.273. 
  2. ^ James T. Dalton, Duane D. Miller, Donghua Yin, Yali He. Selective androgen receptor modulators and methods of use thereof. US Patent 6569896
  3. ^ 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. PMID 19432422. doi:10.1021/jm900280m. 
  4. ^ 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 
  5. ^ 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. PMID 19505196. doi:10.1517/13543770902994397. 
  6. ^ 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. PMC 2630904Freely accessible. PMID 18772237. doi:10.1210/en.2008-0674. 
  7. ^ 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
  8. ^ 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
  9. ^ http://www.vacansoleildcm.co.uk/nieuws/nikita-novikov-provisionally-suspended-after-possible-breach-of-anti-doping-rules.html
  10. ^ http://mmajunkie.com/2016/02/tim-means-pulled-from-ufc-fight-night-83-headliner-after-failed-usada-test
  11. ^ http://www.dpa-international.com/news/sports2/azerbaijans-beji-fails-doping-test-at-european-games-a-45758559.html
  12. ^ http://espn.go.com/boxing/story/_/id/15751796/lucian-bute-tested-positive-draw-vs-badou-jack
  13. ^ "Russian boxer Povetkin tests positive, fight with Canadian Stiverne cancelled – WBC". RT International. Retrieved 2016-12-17. 
  14. ^ http://www.slowtwitch.com/Features/2016_Triathlon_Year_in_Review_6159.html
  15. ^ http://triathlonmagazine.ca/feature/two-american-pro-triathletes-reveal-doping-violations-today/
  16. ^ http://mmajunkie.com/2017/02/tom-lawlor-gets-2-year-suspension-from-usada-for-ostarine