S-23 is a selective androgen receptor modulator (SARM). It binds to the AR (Ki = 1.7 nM) and induces AR-mediated transcriptional activation in CV-1 cells expressing the human receptor when used at a concentration of 10 nM. S-23 increases prostate, seminal vesicle, and levator ani muscle weights in castrated rats. It decreases testicular sperm concentration without reducing mounting behavior or the number of intromissions in intact rats when administered in combination with estradiol benzoate . S-23 (3 mg/kg) also increases preference for sexually active intact males when administered to ovariectomized female rats.