Imtesty posted a great review on BRD4 drug discovery published in the Journal of Medicinal Chemistry in early 2017. Here is another great review entitled "BET inhibitors: a novel epigenetic approach" published recently in the Annals of Oncology. They didn't sugar coat things in that review and are not too optimistic that single agent BET inhibitor therapy will have much clinical success in oncology. However, they were very excited about combination therapy potential including a shout out to Zenith's ZEN-3694 and Gilead's GS-5829 mCRPC trials w/ enzalutamide:

"We eagerly await the findings of two ongoing studies that pair a BET inhibitor with enzalutamide in patients with metastatic CRPC (Table 1) which will help clarify if androgen and BET inhibition in combination will provide an additive effect or even induce cytotoxicity."