Ostarine

Potential Health Benefits

• Improves muscle mass and strength [1-8]
• Reduces overall body fat [9-10]
• Maintains bone strength and quality [11-12]
• Improves sexual function [13-15]
• Improves cholesterol profile [16-18]
• Improves blood sugar level [19-22]
• Prevents breast cancer [23-26]

What is Ostarine?

Ostarine, also known as enobosarm or MK-2866, is a widely known nonsteroidal selective androgen receptor modulator (SARM). It is commonly used by athletes to increase lean muscle mass and bone strength. Aside from improving athletic performance and exercise endurance, ostarine is also used for the treatment of involuntary weight loss due to debilitating medical conditions.

How Ostarine Works

Ostarine belongs to a class of drugs called selective androgen receptor modulators (SARMs). It works by attaching to proteins in the body known as androgen receptors. By binding to these receptors, ostarine stimulates the muscles to grow. This process also leads to bone remodeling.

Chemical Structure of Ostarine

Research on Ostarine

Improves Muscle Mass and Strength

Numerous studies found that ostarine can help increase muscle mass and strength:

1. A study showed that ostarine administration resulted in increased lean muscle mass and decreased fat mass. [1]
2. In 3-month old Sprague-Dawley rats, ostarine showed beneficial effects on muscle formation. [2]
3. In elderly men and postmenopausal women, ostarine significantly improved total lean body mass and physical function. [3]
4. A review of studies showed that ostarine could reverse the hypogonadal-related decline of muscle mass and bone density. [4]
5. In cancer patients, daily oral administration of ostarine resulted in improved lean body mass. [5]
6. A review of studies showed that ostarine treatment resulted in improved muscle mass. [6]
7. In patients with muscle wasting caused by cancer, the administration of ostarine increased muscle mass. [7-8]

Reduces Overall Body Fat

Evidence suggests that ostarine has fat-burning properties:

1. A review of studies showed that ostarine increased lean body mass and decreased fat mass in obese and overweight subjects. [9]
2. In a phase 2a study, ostarine was shown to increase lean body mass and decrease body fat percentage. [10]

Maintains Bone Strength and Quality

Evidence found that ostarine can help improve overall bone health:

1. In rats who had surgical removal of the ovaries, ostarine administration had positive effects on early bone healing. [11]
2. In mice who had surgical removal of the testes, ostarine has been shown to be a potential treatment for osteoporosis. [12]

Improves Sexual Function

Studies show that SARMs like ostarine have beneficial effects on sexual function:

1. A review of studies showed that SARMs can treat sexual dysfunction due to hypogonadism (low testosterone). [13]
2. In a castrated rodent model, SARMs ameliorated sexual dysfunction and motor activity deficits. [14]
3. In rats that had surgical removal of the ovaries, SARMs increased sexual motivation, with potency and efficacy comparable with testosterone propionate. [15]

Improves Cholesterol Profile

There’s also evidence supporting that ostarine has beneficial effects on cholesterol levels:

1. In rats who had surgical removal of the ovaries, ostarine treatment resulted in reduced serum cholesterol level. [16]
2. In elderly men and postmenopausal women, ostarine treatment was associated with a reduction in low-density lipoprotein (bad cholesterol). [17]
3. In elderly men and postmenopausal women, total cholesterol level was reduced with ostarine treatment. [18]

Improves Blood Sugar Level

The administration of ostarine has also been shown to reduce high blood sugar levels:

1. In elderly men and postmenopausal women, ostarine alleviated insulin resistance, a condition in which the body does not respond to the effects of insulin (a hormone that lowers blood sugar). [19]
2. Subjects treated with 3 mg/d of ostarine had on average an 11% decline in fasting blood glucose, a 17% reduction in insulin levels, and a 27% reduction in insulin resistance. [20-22]

Prevents Breast Cancer

1. In mice, oral administration of ostarine inhibited tumor growth. [23]
2. In breast cancer patients, the combined treatment of enobosarm and pembrolizumab had modest benefits. [24]
3. A study showed that enobosarm is an effective treatment for breast cancer. [25]
4. In breast cancer patients, enobosarm successfully slowed breast cancer growth. [26]

Associated Side Effects of Ostarine

Ostarine side effects are very uncommon. There have been some side effects associated with the use of this SARM wherein the patient had one of the issues listed below at some point while being on ostarine. However, the issue wasn’t’ confirmed to be caused by the treatment and could have been a coincidence and not related to the use of ostarine. Despite this, it was listed as a side effect associated with ostarine even these associated side effects are very uncommon.
Side effects associated with ostarine may include the following:

• Back pain
• Depression
• Fatigue
• Headache
• Nausea

References

1. Bhasin S. Selective Androgen Receptor Modulators as Function Promoting Therapies. J Frailty Aging. 2015;4(3):121-122. doi:10.14283/jfa.2015.65.
2. Available at https://academic.oup.com/endo/article/151/8/3706/2456888.
3. Roch PJ, Henkies D, Carstens JC, Krischek C, Lehmann W, Komrakova M, Sehmisch S. Ostarine and Ligandrol Improve Muscle Tissue in an Ovariectomized Rat Model. Front Endocrinol (Lausanne). 2020 Sep 17;11:556581. doi: 10.3389/fendo.2020.556581. PMID: 33042018; PMCID: PMC7528560.
4. Dalton JT, Barnette KG, Bohl CE, Hancock ML, Rodriguez D, Dodson ST, Morton RA, Steiner MS. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle. 2011 Sep;2(3):153-161. doi: 10.1007/s13539-011-0034-6. Epub 2011 Aug 2. PMID: 22031847; PMCID: PMC3177038.
5. Christiansen AR, Lipshultz LI, Hotaling JM, Pastuszak AW. Selective androgen receptor modulators: the future of androgen therapy?. Transl Androl Urol. 2020;9(Suppl 2):S135-S148. doi:10.21037/tau.2019.11.02.
6. Dobs AS, Boccia RV, Croot CC, Gabrail NY, Dalton JT, Hancock ML, Johnston MA, Steiner MS. Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial. Lancet Oncol. 2013 Apr;14(4):335-45. doi: 10.1016/S1470-2045(13)70055-X. Epub 2013 Mar 14. PMID: 23499390; PMCID: PMC4898053.
7. Crawford J, Prado CM, Johnston MA, et al. Study Design and Rationale for the Phase 3 Clinical Development Program of Enobosarm, a Selective Androgen Receptor Modulator, for the Prevention and Treatment of Muscle Wasting in Cancer Patients (POWER Trials). Curr Oncol Rep. 2016;18(6):37. doi:10.1007/s11912-016-0522-0.
8. Srinath, R., & Dobs, A. (2014). Enobosarm (GTx-024, S-22): a potential treatment for cachexia. Future oncology (London, England), 10(2), 187–194. https://doi.org/10.2217/fon.13.273.
9. Solomon ZJ, Mirabal JR, Mazur DJ, Kohn TP, Lipshultz LI, Pastuszak AW. Selective Androgen Receptor Modulators: Current Knowledge and Clinical Applications. Sex Med Rev. 2019;7(1):84-94. doi:10.1016/j.sxmr.2018.09.006.
10. Narayanan R, Mohler ML, Bohl CE, Miller DD, Dalton JT. Selective androgen receptor modulators in preclinical and clinical development. Nucl Recept Signal. 2008;6:e010.
11. Komrakova M, Furtwängler J, Hoffmann DB, Lehmann W, Schilling AF, Sehmisch S. The Selective Androgen Receptor Modulator Ostarine Improves Bone Healing in Ovariectomized Rats. Calcif Tissue Int. 2020 Feb;106(2):147-157. doi: 10.1007/s00223-019-00613-1. Epub 2019 Sep 17. PMID: 31531719.
12. Available at https://tau.amegroups.com/article/view/32604/28654.
13. Christiansen AR, Lipshultz LI, Hotaling JM, Pastuszak AW. Selective androgen receptor modulators: the future of androgen therapy?. Transl Androl Urol. 2020;9(Suppl 2):S135-S148. doi:10.21037/tau.2019.11.02.
14. Morimoto, M., Amano, Y., Oka, M., Harada, A., Fujita, H., Hikichi, Y., Tozawa, R., Yamaoka, M., & Hara, T. (2017). Amelioration of sexual behavior and motor activity deficits in a castrated rodent model with a selective androgen receptor modulator SARM-2f. PloS one, 12(12), e0189480. https://doi.org/10.1371/journal.pone.0189480.
15. Jones A, Hwang DJ, Duke CB 3rd, et al. Nonsteroidal selective androgen receptor modulators enhance female sexual motivation. J Pharmacol Exp Ther. 2010;334(2):439-448. doi:10.1124/jpet.110.168880.
16. Narayanan R, Coss CC, Dalton JT. Development of selective androgen receptor modulators (SARMs). Mol Cell Endocrinol. 2018;465:134-142. doi:10.1016/j.mce.2017.06.013.
17. Komrakova M, Furtwängler J, Hoffmann DB, Lehmann W, Schilling AF, Sehmisch S. The Selective Androgen Receptor Modulator Ostarine Improves Bone Healing in Ovariectomized Rats. Calcif Tissue Int. 2020 Feb;106(2):147-157. doi: 10.1007/s00223-019-00613-1. Epub 2019 Sep 17. PMID: 31531719.
18. Narayanan R, Mohler ML, Bohl CE, Miller DD, Dalton JT. Selective androgen receptor modulators in preclinical and clinical development. Nucl Recept Signal. 2008;6:e010. doi:10.1621/nrs.06010.
19. Dalton JT, Barnette KG, Bohl CE, et al. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle. 2011;2(3):153-161. doi:10.1007/s13539-011-0034-6.
20. Dalton J. T. Development and Potential Uses of Selective Androgen Receptor Modulators (SARMs). American Society of Andrology. 2007a.
21. Dalton J. T., Mukherjee A., Zhu Z., Kirkovsky L., Miller D. D. Discovery of nonsteroidal androgens. Biochem Biophys Res Commun. 1998;244:1–4.
22. Dalton JT, Barnette KG, Bohl CE, et al. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle. 2011;2(3):153-161. doi:10.1007/s13539-011-0034-6.
23. Narayanan R, Ahn S, Cheney MD, et al. Selective androgen receptor modulators (SARMs) negatively regulate triple-negative breast cancer growth and epithelial:mesenchymal stem cell signaling. PLoS One. 2014;9(7):e103202. Published 2014 Jul 29. doi:10.1371/journal.pone.0103202.
24. Yuan Y, Lee JS, Yost SE, Frankel PH, Ruel C, Egelston CA, Guo W, Gillece JD, Folkerts M, Reining L, Highlander SK, Robinson K, Padam S, Martinez N, Tang A, Schmolze D, Waisman J, Sedrak M, Lee PP, Mortimer J. A Phase II Clinical Trial of Pembrolizumab and Enobosarm in Patients with Androgen Receptor-Positive Metastatic Triple-Negative Breast Cancer. Oncologist. 2021 Feb;26(2):99-e217. doi: 10.1002/onco.13583. Epub 2020 Nov 24. PMID: 33141975; PMCID: PMC7873338.
25. Ponnusamy S, Asemota S, Schwartzberg LS, et al. Androgen Receptor Is a Non-canonical Inhibitor of Wild-Type and Mutant Estrogen Receptors in Hormone Receptor-Positive Breast Cancers. iScience. 2019;21:341-358. doi:10.1016/j.isci.2019.10.038.
26. Christiansen AR, Lipshultz LI, Hotaling JM, Pastuszak AW. Selective androgen receptor modulators: the future of androgen therapy?. Transl Androl Urol. 2020;9(Suppl 2):S135-S148. doi:10.21037/tau.2019.11.02.