MK2866

MK-2866, also known as enobosarm and marketed as Ostarine, is a non-steroidal selective androgen receptor modulator (SARM). It was developed for potential treatment of muscle wasting and osteoporosis, with the aim of providing anabolic effects on muscle and bone while limiting androgenic effects in other tissues.

The compound binds to androgen receptors and exhibits tissue-selective activity. In clinical studies for cancer-related cachexia and other conditions, MK-2866 showed increases in lean body mass and some improvements in physical function in some participants, but results were variable and did not lead to regulatory approval.

MK-2866 is not approved by major regulatory authorities such as the FDA or EMA for any medical indication and is not approved for human use outside of clinical trials. It has been studied in Phase II/III trials, but safety and efficacy concerns have limited its development.

Because of its potential to enhance muscle mass, the substance has appeared on sports anti-doping lists since the late 2000s. Reported adverse effects in trials include suppression of endogenous testosterone and changes in liver enzymes; long-term safety data are limited.

In research contexts, MK-2866 is supplied as a research chemical and is not intended for human consumption.