YK11 is one of the newest SARMS to be developed. Due to its infancy, Yk11 has never passed the preclinical development stage and has never been tested on animals or humans. YK-11 is a steroidal selective androgen receptor modulator (SARM) and myostatin inhibitor that was popularized because of its potential to induct supraphysiological levels of follistatin expression.

Myostatin is a type of myokine protein that is the main genetic component that regulates muscle growth potential. Theoretically, YK11 would increase levels of follistatin, a unique type of protein found in the muscle cells which binds to and inhibits the actions of myostatin in the body. More follistatin equals less myostatin, and less myostatin means more muscle. In vitro cellular studies conducted on YK11 confirm that it has an anabolic effect on muscle tissue which is mediated through androgen receptor activation and induction of Follistatin expression.