What Is MK-2866 (Ostarine)?
MK-2866, designated in the scientific literature as Ostarine or Enobosarm, is a non-steroidal selective androgen receptor modulator (SARM) developed by GTx Inc. in the late 1990s. The compound was designed to investigate whether tissue-selective androgen receptor activation could produce anabolic effects in skeletal muscle and bone without the broad androgenic activity associated with classical anabolic steroids. MK-2866 is one of the earliest and most extensively characterised SARMs in the pharmacological record, with a research history spanning multiple Phase I and Phase II clinical trials.
For the purposes of this guide, all discussion of MK-2866 refers to its role as an in-vitro research compound and investigational substance in laboratory settings. It is not approved by the Therapeutic Goods Administration (TGA) or any other regulatory body for human consumption or clinical application.
Chemical Classification and Structure
MK-2866 belongs to the arylpropionamide class of SARMs. Its molecular formula is C19H14F3N3O3, and its molecular weight is 389.33 g/mol. Unlike steroidal androgens, which share a four-ring steroid backbone, MK-2866 achieves androgen receptor binding through a non-steroidal scaffold — a structural characteristic that underlies its tissue selectivity and distinguishes it from testosterone and its derivatives.
The compound is a full agonist at androgen receptors in skeletal muscle and bone tissue. Its binding affinity for the androgen receptor (AR) is well-documented in the peer-reviewed literature, and its pharmacokinetic profile — including oral bioavailability, half-life, and metabolic pathways — has been characterised across multiple preclinical and early-phase clinical studies.
Mechanism of Action
MK-2866 exerts its effects through direct, selective binding to the androgen receptor. When MK-2866 binds to the AR, it induces a conformational change in the receptor’s ligand-binding domain. This altered conformation recruits co-activator proteins selectively — a process that differs from classical androgen-receptor binding and is the structural basis for the tissue selectivity that defines SARMs as a pharmacological class.
In skeletal muscle cells, AR activation by MK-2866 promotes anabolic gene transcription pathways associated with protein synthesis and myocyte maintenance. In bone tissue, AR binding contributes to osteoblast activation and bone mineral density signalling. Critically, in vitro and preclinical in vivo data have consistently shown that MK-2866’s anabolic effect-to-androgenic-effect ratio is substantially higher than that of testosterone, indicating preferential activity in target tissues.
This mechanistic selectivity is what drove GTx’s original therapeutic hypothesis: that a compound like MK-2866 could be used to address skeletal muscle wasting in conditions such as cancer cachexia, osteoporosis, and age-related sarcopenia, while avoiding androgenic complications in non-target tissues. Whether this hypothesis has been validated in clinical trials remains an active area of pharmacological discussion.
Clinical Research History
MK-2866 has one of the most substantial clinical research histories among SARMs. GTx and subsequent investigators have completed multiple Phase I and Phase II trials, providing a body of human pharmacology data that supports its ongoing relevance as a research compound. Key studies investigated its effects on lean body mass, physical function, and bone mineral density in populations including cancer patients, postmenopausal women, and elderly men with muscle wasting.
Phase I studies characterised the compound’s pharmacokinetics in healthy volunteers, establishing its oral bioavailability, plasma half-life (approximately 24 hours), and metabolic profile. Phase II trials in specific patient populations reported statistically significant effects on lean mass and physical performance, though the clinical development pathway for a regulated therapeutic has not yet reached commercialisation.
The published clinical record makes MK-2866 one of the most cited SARMs in pharmacological literature, and its well-characterised binding kinetics and pharmacokinetic profile make it a valuable reference compound for androgen receptor research.
Formats Available for Research
MK-2866 is available from Buy Ostarine Australia in three formats, each suited to different research applications:
Powder
Lyophilised powder provides maximum flexibility for assay preparation. The powder form can be reconstituted in DMSO or ethanol for use in cell-based assays, and allows precise preparation of working solutions at researcher-specified concentrations. Our MK-2866 Powder 1g is supplied at ≥99% purity with molecular formula confirmation.
Liquid Solutions
Pre-dissolved liquid solutions in pharmaceutical-grade PEG-400 are available at three concentrations: 20mg/mL, 25mg/mL, and 30mg/mL. Liquid format is suited to applications requiring consistent, ready-to-use solutions without additional preparation steps. Each concentration is available in 30mL through 150mL volumes.
Capsules
MK-2866 capsules are available in sizes from 5mg to 5g total and offer accurate per-unit quantity precision, which can be advantageous in studies requiring consistent compound quantities across experimental replicates. Capsules are manufactured in a controlled environment with fill weight verification.
Purity and Quality Standards
The reliability of any research outcome depends on compound purity. MK-2866 used in in-vitro research must meet a defined purity threshold to ensure that observed experimental effects reflect the target compound’s activity rather than contaminants or structural analogues. The accepted standard in research-grade SARM supply is ≥99% purity by HPLC (high-performance liquid chromatography).
At Buy Ostarine Australia, every batch of MK-2866 is independently tested by an accredited third-party analytical laboratory before being made available. Our testing protocol includes:
- HPLC purity analysis — confirms compound purity to a minimum of 99%
- Mass spectrometry identity confirmation — verifies molecular weight and fragmentation pattern against MK-2866 reference standards
- Independent retesting — all testing is commissioned independently of our suppliers; we do not accept manufacturer-provided CoA documentation alone
Certificates of Analysis for all current and archived batches are available on our Lab Testing page, indexed by batch number. Your order confirmation includes the batch reference corresponding to your shipment.
Storage and Stability
MK-2866 is a stable compound under appropriate storage conditions. General guidance by format:
- Powder: Room temperature (15–25°C), sealed, away from light and moisture. For archival storage: −20°C. Estimated shelf life: 24 months.
- Liquid solutions: Room temperature (15–25°C), sealed, away from direct light. Do not freeze. Estimated shelf life: 24 months. Gentle warming resolves crystallisation.
- Capsules: Room temperature (15–25°C), dry environment, away from light and humidity. Do not freeze.
Regulatory and Compliance Context (Australia)
In Australia, MK-2866 is classified as a Schedule 4 substance under the Therapeutic Goods Act, meaning it requires a valid prescription for lawful supply in a clinical context. As a research compound, it may be supplied for in-vitro laboratory purposes by licensed suppliers to qualified researchers operating within lawful research frameworks.
All products sold by Buy Ostarine Australia are supplied strictly for in-vitro laboratory and research purposes. They are not approved for human consumption, clinical use, or veterinary application. Buyers confirm at the point of purchase that they are qualified researchers accessing these compounds for lawful research purposes only.
For further reading on COA documentation and purity verification, see our guide to verifying research compound COAs. For format selection guidance, see MK-2866 formats for research.