Ostarine – often referred to as MK-2866 or Enobosarm – is a Selective Androgen Receptor Modulator (SARM) developed by GTx, Inc. for conditions like muscle wasting and osteoporosis.
“Ostarine represents one of the most clinically advanced SARMs, with multiple Phase II trials conducted in cancer-related cachexia and age-related sarcopenia.” – Journal of Cachexia, Sarcopenia and Muscle
Unlike anabolic steroids, Ostarine was designed to provide anabolic effects in muscle and bonewithout strongly affecting tissues such as the prostate.
Table 1: Core Chemical & Research Attributes of Ostarine (MK-2866)
double exposure of SARMS stethoscope laboratory test tube magnifying glass and medical information form on desk medical research diagnosis medical report record and history patient concept blue tone
Clinical research has explored Ostarine for:
Cancer cachexia: Phase II trials showed measurable improvements in lean body mass and physical performance.
Sarcopenia (age-related muscle decline): Demonstrated anabolic benefits in older populations without typical steroid complications.
Osteoporosis & rehabilitation: Investigated for its bone-preserving potential.
Table 2: Key Clinical Studies of Ostarine (Enobosarm / MK-2866)
Study Focus
Title & Details
Link
1. Elderly / Postmenopausal (Phase II)
The selective androgen receptor modulator GTx‑024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women – Phase II, double‑blind, placebo‑controlled trial showing dose‑dependent increases in lean body mass and physical function
Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial – Improvements in lean mass and stair-climb power in cancer-induced muscle wasting
Activity and safety of enobosarm … in androgen receptor-positive, estrogen receptor-positive, HER2-negative advanced breast cancer – Phase II, showing anti-tumor activity and safety profile
Veru’s Phase 2b QUALITY study: Enobosarm preserved lean mass and improved body composition in patients receiving WEGOVY® (semaglutide) for weight reduction
Approval status: Not licensed by the FDA, EMA, or MHRA.
Research-only supply: Legally sold in the UK as a research chemical (must comply with REACH and laboratory handling standards).
Sporting ban: Listed on the b.
Ostarine was originally developed to help patients with muscle wasting, cachexia, and osteoporosis. In controlled trials, it showed measurable benefits in lean mass and function.
However, these studies were short-term (typically 12 weeks or less) and conducted under strict medical supervision. Long-term safety data in humans is not available.
While Ostarine is often marketed as a “safer alternative” to anabolic steroids, it is not risk-free. Documented or suspected side effects include:
Hormonal suppression: decreased natural testosterone production
Unknown long-term effects due to lack of large-scale studies
“Although SARMs such as ostarine are promoted as safer than steroids, they are not without risks, including hepatotoxicity and endocrine disruption.” – U.S. Food & Drug Administration (FDA), 2017 warning letter
Table 3: Legal Status of Ostarine (Enobosarm / MK-2866) by Country
Country
Legal Status Summary
United States
Considered an unapproved investigational drug; cannot be marketed as a dietary supplement or drug. Also prohibited in sports.
United Kingdom
Not approved for human consumption; though widely accessible online, it remains illicit.
General (Global View)
Classified as an investigational drug and not approved globally. It’s also listed as a banned substance in competitive sports under WADA’s Anabolic Agents category.
US Military / DoD (Implication)
SARMs like Ostarine are considered unapproved drugs, illegal as dietary supplements, and prohibited for military service members.
United States (Medical Context)
Remains an investigational agent, with no FDA approval for any medical use, but still appearsin some dietary supplements despite regulations.
“Ostarine (Enobosarm) is prohibited at all times (in- and out-of-competition) as an anabolic agent.” – WADA, 2025
Key Takeaways for Researchers
Ostarine = nonsteroidal SARM with muscle- and bone-specific effects.
Considered a reference compound for studying anabolic pathways.
Favorable short-term trial data, but long-term human safety remains uncertain.
Legal acquisition requires research compliance with chemical regulations.
Ostarine (MK-2866) at a Glance
Property
Detail
Code Name
MK-2866 / Enobosarm
Compound Type
Nonsteroidal SARM
Primary Research Use
Muscle wasting, osteoporosis, sarcopenia
Mechanism
Selective AR binding → lean mass & bone preservation
Clinical Development
Phase II trials (cachexia, sarcopenia)
Legal Status (UK)
Not approved for human use, sold as research chemical
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What is Ostarine (MK-2866)? A Complete Guide for UK Researchers in 2025
Overview
Ostarine – often referred to as MK-2866 or Enobosarm – is a Selective Androgen Receptor Modulator (SARM) developed by GTx, Inc. for conditions like muscle wasting and osteoporosis.
Unlike anabolic steroids, Ostarine was designed to provide anabolic effects in muscle and bonewithout strongly affecting tissues such as the prostate.
Table 1: Core Chemical & Research Attributes of Ostarine (MK-2866)
Mechanism of Action
The research appeal of Ostarine lies in its selectivity:
Research Applications
Clinical research has explored Ostarine for:
Important: Ostarine is not approved for medical use. All applications remain strictly investigational.
Table 2: Key Clinical Studies of Ostarine (Enobosarm / MK-2866)
Safety & Legal Context
Ostarine was originally developed to help patients with muscle wasting, cachexia, and osteoporosis. In controlled trials, it showed measurable benefits in lean mass and function.
However, these studies were short-term (typically 12 weeks or less) and conducted under strict medical supervision. Long-term safety data in humans is not available.
While Ostarine is often marketed as a “safer alternative” to anabolic steroids, it is not risk-free. Documented or suspected side effects include:
Table 3: Legal Status of Ostarine (Enobosarm / MK-2866) by Country
Key Takeaways for Researchers
Ostarine (MK-2866) at a Glance
How to find the best company for SARMS in the UK
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