metribolone metribolone metribolone (developmental code r1881, also known as methyltrienolone) is a synthetic and orally active anabolic–androgenic steroid (aas) and a 17α-alkylated nandrolone (19-nortestosterone) derivative which was never marketed for medical use but has been widely used in scientific research as a hot ligand in androgen receptor (ar) ligand binding assays (lbas) and as a photoaffinity label for the ar. more precisely, metribolone is the 17α-methylated derivative of trenbolone. it was investigated briefly for the treatment of advanced breast cancer in women in the late 1960s and early 1970s, but was found to produce signs of severe hepatotoxicity at very low dosages, and its development was subsequently discontinued. metriboloneclinical dataother namesmethyltrienolone, 17α-methyltrenbolone; r1881; r-1881; ru-1881; nsc-92858; 17α-methyl-19-nor-δ9,11-testosterone; 17α-methylestra-4,9,11-trien-17β-ol-3-oneroutes ofadministrationby mouthdrug classandrogen; anabolic steroid; progestogenidentifiers iupac name (8s,13s,14s,17s)-17-hydroxy-13,17-dimethyl-1,2,6,7,8,14,15,16-octahydrocyclopentaphenanthren-3-one cas number965-93-5 ypubchem cid261000iuphar/bps2857chemspider229099 yunii2c323egi97keggc14257 ychebichebi:379896 ychemblchembl166444 ycomptox dashboard (epa)dtxsid8034162 echa infocard100.190.113 chemical and physical dataformulac19h24o2molar mass284.399 g·mol−13d model (jsmol)interactive image smiles c1(cc21(c=cc3=c4ccc(=o)c=c4cc23)c)o inchi inchi=1s/c19h24o2/c1-18-9-7-15-14-6-4-13(20)11-12(14)3-5-16(15)17(18)8-10-19(18,2)21/h7,9,11,16-17,21h,3-6,8,10h2,1-2h3/t16-,17+,18+,19+/m1/s1 nkey:cccijqprixgqoe-xwsjacjdsa-n n (verify) medical uses metribolone was never approved for medical use, a situation unlikely to change given its liver toxicity even at low doses. it was studied for the potential treatment of advanced breast cancer in women but development was abandoned. side effects