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Ost3.6
Ostarine (MK-2866 / Enobosarm) Research
Mostly mechanism / observationalLimited safety
7 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
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 mixed-quality randomised trials published 2011–2025 with a typical study size of 120 participants.
Based on 7 studies · 2 RCTs · 122 total participants
Confidence
Low
By outcome
Lean mass & body composition
Mostly mechanism / observational7 studies
Testosterone & HPTA suppression
Mostly mechanism / observational7 studies
Liver injury
Mostly mechanism / observational3 studies
Safety profile
Mostly mechanism / observational3 studies
Active research area
4 studies in the last 5 years
201120182025
1RCTn=120 · medium study2011
GTx-024 treatment resulted in dose-dependent increases in total lean body mass that were statistically significant (P < 0.001, 3 mg vs. placebo) and clinically meaningful.
Dalton JT, Barnette KG, Bohl CE, Hancock ML, Rodriguez D, Dodson ST, et al. · Journal of cachexia, sarcopenia and muscle (2011)
The foundational human efficacy trial — a 12-week double-blind, placebo-controlled phase-2 RCT in 120 healthy elderly men and postmenopausal women
Enobosarm produced dose-dependent, statistically significant increases in total lean body mass by DXA, with improvements in physical function and insulin resistance
Adverse-event incidence was similar to placebo over the 12-week study — the basis for advancing into the phase-3 cachexia program
At 24 weeks, 16 (32%, 95% CI 20-47) of 50 in the 9 mg group and 15 (29%, 17-43) of 52 in the 18 mg group had clinical benefit.
Palmieri C, Linden H, Birrell SN, Wheelwright S, Lim E, Schwartzberg LS, et al. · The Lancet. Oncology (2024)
A randomised phase-2 trial of oral enobosarm (9 mg vs 18 mg daily) as a hormonal agent in AR-positive, ER-positive, HER2-negative advanced breast cancer
Showed a modest clinical-benefit rate at 24 weeks (~29-32%) — an investigational oncology use distinct from the body-composition reputation
Drug-related grade 3-4 adverse events occurred, most frequently increased hepatic transaminases — consistent with the compound's hepatic signal
SARM preclinical and clinical studies reported significant increases in lean body mass and side effects-including bone remodeling, testosterone suppression, and kidney, liver, and prostate enlargement.
Vasireddi N, Hahamyan HA, Gould HP, Gregory AJM, Gausden EB, Dodson CC, et al. · The American journal of sports medicine (2025)
A PRISMA systematic review of 72 articles on athlete SARM use — the top-of-pyramid synthesis of the harms
Confirms SARMs raise lean body mass but cause testosterone (HPTA) suppression and liver, kidney and prostate effects; case reports describe drug-induced liver injury, myocarditis and tendon rupture
SARMs have no FDA-approved use; estimated athlete prevalence 1-3%, with users often believing the compounds are legal
Only 52% contained selective androgen receptor modulators and many were inaccurately labeled ... most products contained unapproved drugs and substances.
Van Wagoner RM, Eichner A, Bhasin S, Deuster PA, Eichner D · JAMA (2017)
Counter-evidence on product quality: chemical analysis of 44 products sold online as SARMs (including andarine/S-4)
Only 52% actually contained a SARM; many were inaccurately labeled and contained unapproved drugs and other substances
Directly documents that what is sold as andarine is frequently not andarine, with unknown content and purity
The POWER trials are two identically designed randomized, double-blind, placebo-controlled, multicenter, and multinational phase 3 trials to assess the efficacy of enobosarm for the prevention and treatment of muscle wasting in subjects initiating first-line chemotherapy for non-small-cell lung cancer (NSCLC).
Crawford J, Prado CM, Johnston MA, Gralla RJ, Taylor RP, Hancock ML, et al. · Current oncology reports (2016)
Documents the pivotal phase-3 POWER 1 and POWER 2 program — enobosarm 3 mg once daily vs placebo in NSCLC patients, with co-primary endpoints of lean body mass (DXA) and physical function (stair-climb power)
FDA-negotiated responder analysis: lean-mass response = no LBM loss; function response = ≥10% improvement in stair-climb power
Honest nuance: enobosarm increased lean body mass but did not consistently meet the physical-function co-primary endpoint in the program, and it was not approved for cachexia
He had previously taken the SARM Enobosarm (also known as Ostarine) for muscle-building purposes ... Our case demonstrates that SARMs can cause severe liver injuries not prominently mentioned in safety data sheets.
Mertens JE, Bömmer MTC, Regier MB, Gabriëls G, Pavenstädt H, Grünewald I, et al. · Zeitschrift fur Gastroenterologie (2024)
Mandatory counter-evidence on the dominant grey-market use: a previously healthy 24-year-old man developed severe cholestatic jaundice (bilirubin >30 mg/dL) after taking ostarine to build muscle
Required molecular adsorbent recirculation system (MARS) albumin dialysis; bilirubin normalised only ~6 months after first intake
Liver biopsy showed bland hepatocellular cholestasis; the authors stress these harms are not prominently mentioned on product safety sheets
We report two cases of liver injury in young men who used ligandrol and/or ostarine for a few weeks ... Histological evidence showed predominantly cholestatic injury with canalicular bile plugs, ductopenia, and mild hepatocellular damage.
Koller T, Vrbova P, Meciarova I, Molcan P, Smitka M, Adamcova Selcanova S · World journal of clinical cases (2021)
Two young men developed acute cholestatic liver injury after using ligandrol and/or ostarine for a few weeks, often with 'post-cycle therapy'
Clinical picture dominated by jaundice and fatigue; histology showed canalicular bile plugs, ductopenia, and mild hepatocellular damage
Both recovered after ~3 months; the off-target hepatotoxic effects of SARMs are emphasised against their misuse by amateur athletes