Bromodomain and extraterminal domain (BET) proteins are epigenetic readers that regulate gene expression and are involved in cancer pathogenesis. Over the last years, several BET inhibitors have been developed and clinically tested. Results from the first clinical trials show limited single-agent activity in a small subset of patients with hematologic malignancies and in NUT carcinoma. Adverse events have been observed and may limit treatment compliance. Here, we review the preclinical rationale for targeting BET proteins in cancer and the preliminary results from clinical trials, and outline future directions for the use of BET inhibitors as antitumor agents.

Significance: BET inhibitors represent a new class of anticancer agents. Results from the first clinical trials confirm the antitumor potential of BET inhibitors, but their efficacy as single agents seems to be limited. Based on preclinical data, combination therapies with other anticancer agents and the development of a new generation of compounds may open new possibilities for targeting BET proteins as effective anticancer strategies. Cancer Discov; 8(1); 24–36. ©2017 AACR.