trioxifene trioxifene trioxifene (inn) (developmental code name ly-133,314), or as the salt trioxifene mesylate (usan), is a selective estrogen receptor modulator (serm) with competitive binding activity against estradiol for the erα and antagonistic activity against erα-mediated gene expression, that was under preclinical and clinical development by eli lilly and company for breast cancer and prostate cancer, but was abandoned.: 11 its affinity for the rat estrogen receptor was reported to be 20% relative to estradiol. trioxifeneclinical dataother namesly-133,314routes ofadministrationoralatc codenoneidentifiers iupac name -methanone cas number63619-84-1 68307-81-3 (mesylate)pubchem cid50139chemspider45471uniir0130f043hcomptox dashboard (epa)dtxsid30212997 chemical and physical dataformulac30h31no3molar mass453.582 g·mol−1