Lilopristone (INN; development codes ZK-98734 and ZK-734) is a synthetic, steroidal antiprogestogen with additional antiglucocorticoid activity which was developed by Schering and was patented in 1985. It is described as an abortifacient and endometrial contraceptive. The drug differs from mifepristone only in the structure of its C17ñ side chain, and is said to have much reduced antiglucocorticoid activity in comparison.