▁ ▁Mechan ism ▁of ▁action ▁Similarly ▁to ▁tam ox ifen , ▁a ▁SER M , ▁br il an estr ant ▁shows ▁some ▁capacity ▁to ▁activ ate ▁the ▁ER ▁in ▁certain ▁context s ▁and ▁poss esses ▁weak ▁est ro gen ic ▁activity ▁in ▁the ▁rat ▁u ter us , ▁and ▁unlike ▁ful vest rant , ▁which ▁is ▁currently ▁the ▁only ▁SER D ▁to ▁have ▁been ▁market ed , ▁br il an estr ant ▁is ▁not ▁a ▁ster oid ▁and ▁is ▁or ally ▁bio available ▁and ▁does ▁not ▁need ▁to ▁be ▁admin ister ed ▁by ▁intr am us cular ▁injection . ▁Br il an estr ant ▁has ▁been ▁found ▁to ▁be ▁active ▁in ▁tam ox ifen - ▁and ▁ful vest rant - res istant ▁in ▁vit ro ▁models ▁of ▁human ▁breast ▁cancer . ▁Side ▁effects ▁observed ▁in ▁clin ical ▁studies ▁of ▁br il an estr ant ▁thus ▁far ▁have ▁included ▁di arr he a , ▁n ause a , ▁and ▁fat igue ▁of ▁mostly ▁m ild - to - mod er ate ▁sever ity . ▁ ▁Br il an estr ant ▁is ▁a ▁struct ural ▁analog ue ▁of ▁et ac st il , ▁an ▁earlier ▁combined ▁SER M ▁and ▁SER D ▁that ▁was ▁abandoned ▁in ▁ 2 0 0 1 ▁for ▁commercial ▁reasons . ▁ ▁See ▁also ▁ ▁List ▁of ▁investig ational ▁h orm onal ▁agents ▁§ ▁Est ro gen ics ▁ ▁B az ed ox if ene ▁ ▁E lac estr ant ▁ ▁References ▁ ▁External ▁links ▁ ▁G DC - 0 8 1