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Ostarine (MK-2866, enobosarm, GTx-024, S-22) — selective androgen receptor modulator (SARM)
A non-steroidal SARM (enobosarm / MK-2866) developed for muscle wasting and cancer cachexia. Real, large randomized trials show it genuinely adds lean body mass — but it has NEVER been approved: the pivotal cancer-cachexia program met its lean-mass endpoints while missing physical-function endpoints, so a durable functional benefit is unproven. Sold widely as a grey-market 'body-recomp' research chemical, it carries documented drug-induced liver injury, HDL/lipid suppression, and testosterone (HPTA) suppression, is banned by WADA, and the products sold online are frequently mislabelled. Real anabolic signal, unproven function, real harms.
Research compound — not a dietary supplement
Ostarine (MK-2866 / Enobosarm) is a research compound, not a regulated dietary supplement. It is sold for research or off-label use. The evidence below is largely preclinical (animal and in-vitro) or early-stage, so no evidence score is assigned. This page is provided for transparency and education — it is not a recommendation to use. Consult a qualified healthcare provider, and be aware that purity, dosing, and legal status vary by jurisdiction.
What the evidence says
Most Ostarine (MK-2866 / Enobosarm) studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality randomised trials published 2011–2025 with a typical study size of 120 participants.
Based on 7 studies · 2 RCTs · 164 total participants
Confidence
Low confidenceBy outcome
Ostarine (enobosarm) has more real human RCT data than most grey-market compounds — a phase-2 trial and a phase-3 cachexia program both show genuine, dose-dependent lean-body-mass gains. But it is approved for nothing: the pivotal cachexia trials missed their physical-function co-primary endpoint, so a durable functional benefit is unproven. Against the anabolic signal sit documented drug-induced liver injury, HDL/lipid suppression, testosterone (HPTA) suppression, a WADA ban, and a JAMA finding that most products sold as SARMs are mislabelled — so it scores low-emerging.
1 trial ongoing or recruiting · 9 completed on ClinicalTrials.gov
7 of the completed trials have posted results
Registered trials show research momentum for Ostarine (MK-2866 / Enobosarm), not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Aug 2026
Ostarine (MK-2866, also enobosarm, GTx-024 or S-22) is a non-steroidal selective androgen receptor modulator (SARM) — a small molecule that binds the androgen receptor and acts as a tissue-selective agonist, anabolic in muscle and bone while largely sparing prostate and other classically androgenic tissue.
It was developed by GTx as a treatment for muscle wasting and cancer cachexia, and unlike most grey-market 'research chemicals' it actually accumulated real human RCT data.
A 12-week double-blind, placebo-controlled phase-2 trial in 120 healthy elderly men and postmenopausal women (Dalton 2011) showed dose-dependent, statistically significant increases in total lean body mass with improved physical function and insulin resistance — a genuine anabolic signal in people.
That promise drove the pivotal phase-3 POWER 1 and 2 program in non-small-cell-lung-cancer patients (co-primary endpoints of lean body mass by DXA and physical function by stair-climb power): enobosarm increased lean mass but did not consistently hit the responder-defined physical-function co-primary endpoint, so the program did not lead to approval for cachexia.
Enobosarm has since been studied in AR-positive, ER-positive, HER2-negative advanced breast cancer (Palmieri 2024, Lancet Oncology) as an oral hormonal agent with a modest clinical-benefit rate — a different, oncology indication, still investigational.
The honest distinction for this collection: enobosarm reliably adds lean body mass, but a durable clinical/functional benefit has not been proven, and it is approved for nothing.
Against that sit real harms that define the grey-market 'recomp' use: drug-induced liver injury — including severe cholestatic jaundice requiring albumin dialysis — is documented in case reports of young men taking ostarine for muscle building (Mertens 2024; Koller 2021); SARMs suppress HDL cholesterol and the hypothalamic-pituitary-testicular axis (suppressed endogenous testosterone), per a systematic review of athlete SARM use (Vasireddi 2025); and a JAMA chemical analysis (Van Wagoner 2017) found that only 52% of products sold online as SARMs actually contained the labelled SARM, with many containing other unapproved drugs or inaccurate doses — so the user often does not know what they are taking.
Ostarine is on the World Anti-Doping Agency prohibited list and is a common cause of athlete sanctions.
The score reflects genuine, replicated lean-mass gains in humans against an unproven functional benefit, no approval, documented hepatotoxicity, lipid and HPTA suppression, a sport ban, and pervasive product mislabelling.
Enobosarm is a non-steroidal SARM that binds the androgen receptor and acts as a tissue-selective agonist — anabolic in skeletal muscle and bone while largely sparing prostate and other classically androgenic tissue, the basis for the proposed muscle-wasting benefit.
AR activation in muscle drives protein-anabolic gene expression, producing the dose-dependent increases in total lean body mass measured by DXA in human trials — a genuine anabolic effect, distinct from a demonstrated gain in physical function.
Off-target androgen-receptor and hepatic effects underlie the documented harms: drug-induced (often cholestatic) liver injury, suppression of HDL cholesterol, and suppression of the hypothalamic-pituitary-testicular axis with lowered endogenous testosterone.
How Ostarine (MK-2866 / Enobosarm) works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid — not approved, documented liver injury and hormonal/lipid suppression, and no quality-controlled product exists.
Avoid absolutely — WADA-prohibited; ostarine is a common cause of athlete sanctions.
Avoid entirely — androgenic and unstudied in human pregnancy.
Ostarine has caused drug-induced liver injury on its own; combining it with other hepatotoxic agents, alcohol, or 'post-cycle therapy' compounds raises the risk of cholestatic injury.
Stacking androgenic agents compounds HPTA suppression and lipid (HDL) suppression; the combined hormonal and hepatic burden is uncharacterised and likely additive.
SARMs suppress HDL cholesterol, working against lipid management; the net cardiovascular-risk effect of the combination is unstudied.
Tip: Documented in case reports — severe jaundice, in one case requiring albumin dialysis, with months-long recovery. Not on most product labels; there is no safe monitoring framework for grey-market use.
Tip: SARMs suppress endogenous testosterone; recovery is not guaranteed and 'post-cycle therapy' to restore it carries its own documented harms.
Tip: Lowered HDL is a consistent SARM effect that works against cardiovascular health; not reversible while using.
Tip: A JAMA analysis found most online 'SARM' products were mislabelled — wrong identity, other unapproved drugs, or inaccurate doses. Users often do not know what they are ingesting.
Ostarine (MK-2866 / Enobosarm) has an evidence score of 3.6/10 — emerging evidence based on 7 indexed studies. A non-steroidal SARM (enobosarm / MK-2866) developed for muscle wasting and cancer cachexia. Real, large randomized trials show it genuinely adds lean body mass — but it has NEVER been approved: the pivotal cancer-cachexia program met its lean-mass endpoints while missing physical-function endpoints, so a durable functional benefit is unproven. Sold widely as a grey-market 'body-recomp' research chemical, it carries documented drug-induced liver injury, HDL/lipid suppression, and testosterone (HPTA) suppression, is banned by WADA, and the products sold online are frequently mislabelled. Real anabolic signal, unproven function, real harms. Representative study: PMID 39755947.
The commonly studied dose of Ostarine (MK-2866 / Enobosarm) is No legitimate or recommended dose — ostarine is an unapproved grey-market research chemical with documented liver injury, lipid and testosterone suppression, and a sport ban. We do NOT provide a body-composition dosing protocol. For context only, enobosarm was studied at 3 mg once daily orally in the phase-2/phase-3 muscle-wasting trials and 9–18 mg in the breast-cancer trial, under clinical supervision — that is not an endorsement of self-administration.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for Ostarine (MK-2866 / Enobosarm) — consistent daily use matters more than the time of day. There is no validated or endorsed body-composition dosing schedule.
Ostarine (MK-2866 / Enobosarm) should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are drug-induced (cholestatic) liver injury, testosterone (HPTA) suppression, HDL cholesterol / lipid suppression. Use caution if any of these apply to you: Anyone seeking it for body composition — not an approved medicine and not a regulated dietary supplement; an unregulated grey-market research chemical; Pre-existing liver disease or elevated liver enzymes — documented drug-induced (cholestatic) liver injury; Competitive or tested athletes — WADA-prohibited; a common cause of anti-doping sanctions.
Epicatechin
Probably helpsDark chocolate flavanol with consistent human evidence for improved endothelial function and modest blood pressure reduction. Muscle-building claims are not supported in humans.
Beta-Ecdysterone
Mostly mechanism / observationalPhytoecdysteroid that activates the PI3K/Akt pathway; studied for muscle protein synthesis and strength. Non-steroidal, though human strength evidence is limited.
LGD-4033 (Ligandrol)
Mostly mechanism / observationalA nonsteroidal SARM with one small Phase-1 human RCT that did show dose-dependent lean-mass gain over 21 days — but at the cost of suppressed testosterone and HDL cholesterol even at low doses. It was never approved as a medicine, multiple case reports tie it to cholestatic liver injury, internet 'SARM' products are routinely mislabelled, and it is banned by the World Anti-Doping Agency. Sold only as an unregulated grey-market research chemical for body composition.
RAD-140 (Testolone)
Mostly mechanism / observationalAn unapproved selective androgen receptor modulator (SARM) sold grey-market for muscle and body composition. Its anabolic and anti-cancer data are preclinical (cells/animals); the only human studies are a Phase-1 breast-cancer safety trial and case reports of severe liver injury. WADA-banned, suppresses natural testosterone, and grey-market products are routinely mislabeled.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 7 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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