Ostarine (MK-2866)
SARMAlso known as: MK-2866, Enobosarm, GTx-024, S-22
What is Ostarine (MK-2866)?
Ostarine (MK-2866/Enobosarm) is the most commonly detected SARM in both doping tests and supplement adulteration testing. Development by GTx was discontinued after failing Phase 3 clinical trials to improve muscle strength in cancer patients. Over 20 documented liver injury cases.
Why is Ostarine (MK-2866) Banned?
Unapproved drug causing documented liver injury cases. Development abandoned after failing efficacy trials. Most common SARM in doping violations and supplement adulteration.
Health Risks & Side Effects
Health Risk Level
This substance has a moderate risk of overdose and moderate addiction potential.
warningCommon Side Effects
- arrow_rightLiver injury
- arrow_rightTestosterone suppression
- arrow_rightAcne
- arrow_rightHair loss
- arrow_rightMood changes
- arrow_rightGynecomastia
blockContraindications
- arrow_rightLiver disease
- arrow_rightHormone-sensitive conditions
- arrow_rightWomen (virilization risk)
- arrow_rightCompetitive athletes
How Does Ostarine (MK-2866) Work?
Selective Androgen Receptor Modulator that binds to androgen receptors primarily in muscle and bone tissue. Despite claimed selectivity, causes significant testosterone suppression requiring PCT.
History
Developed by GTx Inc. for cancer-related muscle wasting. Failed Phase 3 clinical trials. Most detected SARM globally with over 230 positive doping tests since 2012. Frequently found as undeclared adulterant in supplements.
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Research articles and educational resources
Overview
Enobosarm
Enobosarm, also formerly known as ostarine and by the developmental code names GTx-024, MK-2866, and S-22, is a selective androgen receptor modulator (SARM) which is under development for the treatment of androgen receptor-positive breast cancer in women and for improvement of body composition in people taking GLP-1 receptor agonists like semaglutide. It was also under development for a variety of other indications, including treatment of cachexia, Duchenne muscular dystrophy, muscle atrophy or sarcopenia, and stress urinary incontinence, but development for all other uses has been discontinued. Enobosarm was evaluated for the treatment of muscle wasting related to cancer in late-stage clinical trials, and the drug improved lean body mass in these trials, but it was not effective in improving muscle strength. As a result, enobosarm was not approved and development for this use was terminated. Enobosarm is taken by mouth.
Scientific Research
From PubMed • 3 peer-reviewed studies
Activity and safety of enobosarm, a novel, oral, selective androgen receptor modulator, in androgen receptor-positive, oestrogen receptor-positive, and HER2-negative advanced breast cancer (Study G200802): a randomised, open-label, multicentre, multinational, parallel design, phase 2 trial.
The androgen receptor is a tumour suppressor in oestrogen receptor-positive breast cancer. The activity and safety of enobosarm, an oral selective androgen receptor modulator, was evaluated in women with oestrogen receptor (ER)-positive, HER2-negative, and androgen receptor (AR)-positive disease.
The disordering effect of SARMs on a biomembrane model.
From medicine to sport, selective androgen receptor modulators (SARMs) have represented promising applications. The ability of SARMs to selectively interact with the androgen receptor (AR) indicates that this kind of molecule can interfere with numerous physiological and pathological processes controlled by the AR regulatory mechanism. However, critical concerns in relation to safety and potential side effects of SARMs remain under discussion and investigation. SARMs, being hydrophobic/organic compounds, can be subjected to hydrophobic interactions. In this perspective, we hypothesize that SARMs interact with lipid membranes, producing significant physical and chemical changes that could be associated with several effects that SARMs represent in biological systems. In this context, the effect of SARMs on lipid membranes mediated by non-specific interactions is little explored. Here, we report significant information related to the changes that ostarine, ligandrol, andarine, and cardarine produce in the thermodynamic properties of a lipid biomembrane model. Physical changes and chemical interactions of the systems were investigated by differential scanning calorimetry (DSC), dynamic light scattering (DLS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and theoretical calculations implementing density functional theory (DFT). We demonstrate that ostarine, ligandrol, andarine, and cardarine can strongly interact with a lipid biomembrane model composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and accordingly, these molecules can be incorporated into the polar/hydrophobic regions of the lipid bilayer. By employing theoretical calculations, we gained insights into the possible electrostatic interactions between SARMs and phospholipid molecules, enhancing our understanding of the driving forces behind the interactions of SARMs with lipid membranes. Overall, this investigation provides relevant knowledge related to the biophysical-chemical effects that SARMs produce in biomembrane models and could be of practical reference for promising applications of SARMs in medicine and sport.
Computer-aided (in silico) approaches in the mode-of-action analysis and safety assessment of ostarine and 4-methylamphetamine.
This study exemplifies computer-aided (in silico) approaches in assessing the risks of new psychoactive substances emerging in the European Union. In this work, we (i) consider the potential of Ostarine exhibiting psychoactivity and (ii) anticipate potential activities and toxicities of 4-methylamphetamine.