GTx has initiated a Phase II clinical trial of ostarine, a first-in-class drug. The clinical trial is designed to evaluate the ability of ostarine, a selective androgen receptor modulator (SARM), to build muscle and to promote bone, as well as to assess its safety in both elderly men and postmenopausal women.

Ostarine had an approximately 24-hour half-life in a single-ascending-dose Phase I clinical trial in 96 healthy male volunteers. In a 14 day multiple ascending dose Phase I clinical trial in 48 healthy male volunteers and 23 elderly men, ostarine had positive changes on muscle without clinically detectable side effects on the prostate or the skin.