Telapristone acetate, a selective progesterone receptor modulator (SPRM), was developed for the long-term treatment of symptoms associated with endometriosis and uterine fibroids. It is known, that the progesterone is a steroid hormone that plays an important role in the breast. Deregulation of the progesterone-signaling pathway is implicated in the formation, development, and progression of breast cancer. Thus, the telapristone acetate is studied in phase II clinical trial in stage I-II primary breast cancer. Besides, telapristone acetate participated in phase III clinical trials in pre-menopausal anemic women with symptomatic uterine fibroids. However, FDA terminated these studies because of the safety.