Rosterolone (INN) (developmental code name SH-434), also known as 17α-propylmesterolone or 17β-hydroxy-1α-methyl-17α-propyl-5α-androstan-3-one, is a steroidal antiandrogen that was first reported in 1984 and was developed for topical administration but was never marketed. It has shown some efficacy in the treatment of acne, and in animal models lacks systemic effects with topical application. Rosterolone is a derivative of mesterolone, which, in contrast, is an androgen and anabolic steroid.