em-5854 em-5854 em-5854 is a steroidal antiandrogen which was under development by endoceutics, inc. (formerly endorecherche, inc.) for the treatment of prostate cancer. it was first described in a patent in 2008, and was further characterized in 2012. em-5854 reached phase i/ii clinical trials for the treatment of prostate cancer but development was discontinued in march 2019. em-5854clinical dataother names4-fluoro-17β-hydroxy-17α-estra-1,3,5(10)-triene-3-carbonitriledrug classsteroidal antiandrogenidentifiers iupac name (8r,9s,13s,14s,17r)-4-fluoro-17-hydroxy-13-methyl-17--7,8,9,11,12,14,15,16-octahydro-6h-cyclopentaphenanthrene-3-carbonitrile pubchem cid25015772chemical and physical dataformulac25h27fn2o2molar mass406.501 g·mol−13d model (jsmol)interactive image smiles c12cc3(1cc2(cc4=cc=(c=c4))o)ccc5=c3c=cc(=c5f)c#n inchi inchi=1s/c25h27fn2o2/c1-24-10-6-19-18-3-2-17(15-27)23(26)21(18)5-4-20(19)22(24)7-11-25(24,29)14-16-8-12-28(30)13-9-16/h2-3,8-9,12-13,19-20,22,29h,4-7,10-11,14h2,1h3/t19-,20-,22+,24+,25-/m1/s1key:yklvheradajqqv-ngqkkbaqsa-n the drug acts as a potent and selective competitive antagonist of the androgen receptor (ar). unlike other steroidal antiandrogens like cyproterone acetate, but similarly to nonsteroidal antiandrogens like bicalutamide and enzalutamide, em-5854 is a pure or silent antagonist of the ar and shows no intrinsic partial androgenic activity. em-5854 and its metabolite em-5855 show 3.7-fold and 94-fold higher affinity for the human ar than bicalutamide (0.66% and 17% of the rba of metribolone, respectively, compared to 0.18% for bicalutamide). they also show dramatically increased antiandrogenic potency relative to bicalutamide in in vivo assays. on the basis of the available research, it has been said that em-5854 may possibly have 70- to 140-fold the antiandrogenic potency of bicalutamide in humans. em-5854 and em-5855 show little to no affinity for other steroid hormone receptors including the estrogen, progesterone, and glucocorticoid receptors. em-5854 bears a cyano phenyl group, the structural motif of the nonsteroidal antiandrogens. em-5854 and other ar antagonists at steroid hormone receptors and in ar-dependent cancer cell lines activityspecificsbicafluoh‑fluenzaem‑5854em‑5855 ar rba (%)human0.18na0.170.070.6617 metri = 100%rat0.13na0.070.020.352.6 shionogi cells aa activityki (nm)81nana1702.00.77 lncap cells (psa) aa activity and stim of basal prolifde50 (nm) (inhib at 10−7 m (%))1750(6 ± 10)nana1380(−20 ± 3)127(36 ± 7)66(66 ± 1) stim at 10−7 m (%)0 ± 1nana1 ± 119 ± 129 ± 2 er rba (%)rat (e2 = 100%)0na0000 pr rba (%)rat (prom = 100%)ndna0nd0.2nd gr rba (%)rat (dexa = 100%)0na0<0.100