Testifenon, also known as testiphenon, testiphenone, chlorphenacyl dihydrotestosterone ester, or dihydrotestosterone 17ò-(4-(bis(2-chloroethyl)amino)phenyl)acetate, is a synthetic anabolicâÂÂandrogenic steroid (AAS) and a cytostatic antineoplastic agent (i.e., chemotherapeutic) that was never marketed. It is an androgen ester â specifically, a chlorphenacyl nitrogen mustard ester of dihydrotestosterone (DHT) â and acts as a prodrug of these two components in the body. The drug was developed in Russia as a tissue-selective cytostatic drug for the treatment of various cancers occurring in androgen receptor-expressing tissues that would have reduced side effects and toxicity relative to other chemotherapy drugs.