What Is MK-2866?
MK-2866 is the development code commonly associated with ostarine, a nonsteroidal selective androgen receptor modulator, or SARM. The compound was developed by GTx, Inc. under the name enobosarm and GTx-024. Unlike traditional anabolic-androgenic steroids, which can activate androgen receptors throughout many tissues, a SARM is designed to produce a more tissue-selective response. Ostarine binds to androgen receptors and was investigated primarily for its ability to increase or preserve lean body mass and physical function in settings where muscle loss is clinically important.
Ostarine is often described in online fitness communities as a beginner-friendly SARM because early clinical studies used relatively low doses and reported generally modest adverse effects compared with many anabolic steroids or more potent investigational SARMs. That description should not be confused with regulatory approval or proof of recreational safety. Enobosarm was one of the furthest-along SARMs in clinical development and reached late-stage study for cancer-associated muscle wasting, including Phase 3 programs, but it did not become an approved treatment for bodybuilding, performance enhancement, or routine body recomposition. Interest in recomposition comes from its potential to support lean mass while dieting, but controlled clinical evidence does not establish that recreational users can safely achieve those outcomes.
Online products labeled MK-2866 may not contain pharmaceutical-grade enobosarm. They may be sold as research chemicals, liquids, capsules, or tablets, and independent testing has found substantial variation in identity, concentration, and contamination among unregulated performance-enhancing products. In the United States and many other countries, using or possessing an unapproved product for human consumption may carry legal and medical risks. Anyone considering use should discuss the issue with a qualified clinician rather than relying on vendor instructions, social-media protocols, or anecdotal cycle reports.
Quick Reference
Member reference tables summarize the compound's research parameters.
Research Indications
Research Protocols
As reported in cited literature and research-community logs (see Research Citations below), not a personal dosing recommendation.
This member section describes parameters reported in the research literature.
Peptide Interactions
This member section summarizes reported compound interactions and evidence limitations.
Reported Research Time Points
This member section summarizes reported research time points.
Safety Notes
Included for harm-reduction awareness only, in the event this compound is encountered outside its labeled research use. Inclusion here does not imply RUO Codes endorses, recommends, or instructs human use.
This member section discusses research safety considerations and uncertainties.
Quality Indicators
Research Citations
- The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial
Dalton, J. T., Barnette, K. G., Bohl, C. E., et al., 2011, Journal of Cachexia, Sarcopenia and Muscle - Effect of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial
Dobs, A. S., Boccia, R. V., Croot, C. C., et al., 2013, The Lancet Oncology - Selective androgen receptor modulators: a novel approach to androgen therapy
Basaria, S., 2010, The Journal of Clinical Endocrinology & Metabolism - Selective androgen receptor modulators: the future of androgen therapy
Mohler, M. L., Bohl, C. E., Jones, A., et al., 2009, Endocrine Reviews - Selective androgen receptor modulators: current status and future prospects
Narayanan, R., Mohler, M. L., Bohl, C. E., et al., 2015, Drugs