Performance & GH axis
Ostarine
MK-2866, Enobosarm, GTx-024
Ostarine is a selective androgen receptor modulator — a small molecule, not a peptide — developed for muscle wasting and later for breast cancer. It is not approved anywhere and is widely sold as a research chemical.
Also known as: MK-2866, MK2866, enobosarm, GTx-024
- Status
- Ostarine is a research compound and not approved by the FDA for human use.
- Evidence
- Human trials. Published clinical trials in people report results.
- Half-life
- Approximately 24 hours.
- How it's taken
- Oral, in non-clinical use
- Mechanism
- Anabolic (IGF-1 / myostatin)
- Pathways
- Androgen
How Ostarine works
Ostarine binds the androgen receptor as a partial agonist with tissue selectivity, producing anabolic effects in muscle and bone while causing less activity in prostate and skin than testosterone. The selectivity arises from tissue-specific differences in receptor conformation and coregulator recruitment. Because it is not a substrate for 5-alpha-reductase or aromatase, it does not convert to dihydrotestosterone or estradiol along the classic pathways.
What research has looked at
- Phase 2 trials reported increases in lean body mass and improvement in stair-climb power in cancer cachexia and in healthy elderly participants.
- Oral bioavailability, unlike injectable testosterone esters.
- Less prostatic and androgenic effect than testosterone at doses producing comparable lean mass gain, which was the design goal.
Evidence level: Human trials. Published clinical trials in people report results. These are areas studied or reported, not promised effects.
Reported side effects and risks
- It failed to meet its co-primary endpoints in the POWER Phase 3 trials for cancer cachexia — lean mass improved but physical function did not, the same mass-versus-function dissociation seen with bimagrumab. It has never been approved.
- It suppresses endogenous testosterone production through hypothalamic-pituitary feedback, and recovery is not guaranteed.
- The FDA has issued warnings about SARMs specifically, citing reports of drug-induced liver injury, and has documented elevated transaminases and bilirubin.
- Cases of severe cholestatic liver injury have been reported in users.
- Adverse lipid changes, particularly suppression of HDL cholesterol.
- It is prohibited at all times under the WADA Prohibited List and is a common cause of positive tests, including from contaminated supplements.
- Independent testing has repeatedly found products sold as SARMs to contain different compounds, wrong doses, or unapproved drugs entirely.
Sources
- PubMed research on ostarine enobosarm POWER trial SARM liver · NIH · National Library of Medicine
- DrugBank record for enobosarm · DrugBank
- Active clinical trials for enobosarm · U.S. National Library of Medicine
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Related compounds
Ostarine FAQ
What is Ostarine?
Ostarine is a selective androgen receptor modulator — a small molecule, not a peptide — developed for muscle wasting and later for breast cancer. It is not approved anywhere and is widely sold as a research chemical.
How does Ostarine work?
Ostarine binds the androgen receptor as a partial agonist with tissue selectivity, producing anabolic effects in muscle and bone while causing less activity in prostate and skin than testosterone. The selectivity arises from tissue-specific differences in receptor conformation and coregulator recruitment. Because it is not a substrate for 5-alpha-reductase or aromatase, it does not convert to dihydrotestosterone or estradiol along the classic pathways.
Is Ostarine FDA approved?
No. Ostarine is a research compound and not approved by the FDA for human use. Evidence level: human trials. Published clinical trials in people report results.
What is the half-life of Ostarine?
Reported half-life: Approximately 24 hours.
How is Ostarine taken?
Oral, in non-clinical use.
What side effects have been reported with Ostarine?
Reported in the sources: It failed to meet its co-primary endpoints in the POWER Phase 3 trials for cancer cachexia — lean mass improved but physical function did not, the same mass-versus-function dissociation seen with bimagrumab. It has never been approved; It suppresses endogenous testosterone production through hypothalamic-pituitary feedback, and recovery is not guaranteed; The FDA has issued warnings about SARMs specifically, citing reports of drug-induced liver injury, and has documented elevated transaminases and bilirubin; Cases of severe cholestatic liver injury have been reported in users; Adverse lipid changes, particularly suppression of HDL cholesterol; It is prohibited at all times under the WADA Prohibited List and is a common cause of positive tests, including from contaminated supplements; Independent testing has repeatedly found products sold as SARMs to contain different compounds, wrong doses, or unapproved drugs entirely.
Educational summary compiled from the sources listed above. Not medical advice. Peptide Vault does not sell, source or recommend any compound. Talk to a qualified clinician before starting or changing anything.