Lonaprisan

Lonaprisan (INN, USAN) (developmental code names ZK-230211, BAY 86-5044, ZK-PRA) is a synthetic, steroidal antiprogestogen which was under development by Bayer HealthCare Pharmaceuticals for the treatment of endometriosis, dysmenorrhea, and breast cancer but was discontinued. It is a potent and highly selective silent antagonist of the progesterone receptor (PR). The drug reached phase II clinical trials prior to its discontinuation.