LGD-3303

LGD-3303 is a nonsteroidal, orally bioavailable SARM that binds the androgen receptor with high in vitro affinity (Ki = 0.9 nM) and potently activates AR-mediated transcription (EC50 = 3.6 nM, 134% efficacy relative to dihydrotestosterone), while showing much weaker affinity for the mineralocorticoid, glucocorticoid, and progesterone receptors (Ki = 1261, 581, and 136 nM respectively).

In castrated male rats (an androgen-deficiency model), oral LGD-3303 at 1 mg/kg/day completely prevented loss of levator ani muscle weight and acted as a partial agonist on prostate and preputial gland tissue; local tissue drug concentrations were reportedly higher in prostate than in the more strongly responding levator ani muscle, indicating the tissue selectivity is not explained by differential drug distribution. This is preclinical rodent evidence only and has not been demonstrated in a human clinical study.