mepitiostane mepitiostane mepitiostane, sold under the brand name thioderon, is an orally active antiestrogen and anabolic–androgenic steroid (aas) of the dihydrotestosterone (dht) group which is marketed in japan as an antineoplastic agent for the treatment of breast cancer. it is a prodrug of epitiostanol. the drug was patented and described in 1968. mepitiostaneclinical datatrade namesthioderonother names10364-s; epitiostanol 17β-(1-methoxy)cyclopentyl ether; 17β--2α,3α-epithio-5α-androstaneahfs/drugs.cominternational drug namesroutes ofadministrationby mouthdrug classandrogen; anabolic steroid; androgen ether; antiestrogenatc codenonelegal statuslegal status in general: ℞ (prescription only) identifiers iupac name (1s,2s,4r,8s,11r,12s,15s,16s)-15--2,16-dimethyl-5-thiapentacyclooctadecane cas number21362-69-6 ypubchem cid9909202chemspider8084854 nuniio00404969kkeggd01602 ychemical and physical dataformulac25h40o2smolar mass404.65 g·mol−13d model (jsmol)interactive image smiles c12cc3(1cc2oc4(cccc4)oc)cc53(c6(c5)s6)c inchi inchi=1s/c25h40o2s/c1-23-13-10-19-17(7-6-16-14-20-21(28-20)15-24(16,19)2)18(23)8-9-22(23)27-25(26-3)11-4-5-12-25/h16-22h,4-15h2,1-3h3/t16-,17-,18-,19-,20-,21+,22-,23-,24-/m0/s1 nkey:ivdyzaapolnzkg-kwhraddssa-n n ny (what is this?) (verify) medical uses mepitiostane is used as an antiestrogen and antineoplastic agent in the treatment of breast cancer. it is also used as an aas in the treatment of anemia of renal failure. a series of case reports have found it to be effective in the treatment of an estrogen receptor (er)-dependent meningiomas as well. side effects