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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 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 products sold online may have unreliable identity, strength or quality. 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 9 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 analysis in which only 23 of 44 products sold online as SARMs and bought in 2016 contained any SARM — 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 Nov 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) of 44 products sold online as SARMs and bought in 2016 found that only 23 (52%) contained any SARM, 17 (39%) contained another unapproved drug and only 18 (41%) matched the labelled amount, so a buyer may 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 products that may have unreliable identity, strength or quality.
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: In a JAMA analysis of 44 products sold online as SARMs and bought in 2016, only 23 contained any SARM, 17 contained another unapproved drug and only 18 matched the labelled amount (Van Wagoner 2017). A buyer may not know what they are taking.
Ostarine (MK-2866 / Enobosarm) has an evidence score of 3.6/10 — emerging evidence based on 9 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 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 products sold online may have unreliable identity, strength or quality. Real anabolic signal, unproven function, real harms. Representative study: PMID 39755947.
Dosing for Ostarine (MK-2866 / Enobosarm): No self-directed dose is recommended by SupStack. 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, so check the right dose for you with a healthcare provider.
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. Reported side effects include drug-induced (cholestatic) liver injury, testosterone (HPTA) suppression, HDL cholesterol / lipid suppression. How often they occur is not established for all of them. 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.
What side effects does Ostarine (MK-2866 / Enobosarm) have?Don't take this if…
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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 may have unreliable identity, strength or quality, and it is banned by the World Anti-Doping Agency. Sold only as an unregulated grey-market research chemical for body composition.
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Mostly mechanism / observationalA 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 may have unreliable identity, strength or quality.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 9 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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