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.

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 RBATooltip relative binding affinity 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.