The BET-bromodomain inhibitor OTX015 (MK-8628) was initially developed by Mitsubishi Tanabe Pharma Corporation, but then was licensed by OncoEthix, privately held biotechnology company. OTX015 is a selective bromodomains: BRD2, BRD3, and BRD4 inhibitor and inhibits their binding to AcH4. Bromodomains have an important role in the targeting of chromatin-modifying enzymes to specific sites, including methyltransferases, HATs and transcription factors and regulate diverse biological processes from cell proliferation and differentiation to energy homeostasis and neurological processes. OTX015 has potent antiproliferative activity accompanied by c-MYC down-regulation in several tumor types, and has demonstrated synergism with the mTOR inhibitor everolimus in different models. Oral administration of OTX-015 markedly inhibited tumor growth and reduced tumor volume. OTX015 is currently in Phase 1b studies for the treatment of hematological malignancies and advanced solid tumors such as Triple Negative Breast Cancer, Non-small Cell Lung Cancer, Castrate-resistant Prostate Cancer (CRPC) and Pancreatic Ductal Adenocarcinoma. In addition, OTX015 was in phase II for the treatment of Glioblastoma Multiforme, but there were not detected clinical activity of the drug in the treatment populations and trial was closed.

Mivebresib (ABBV-075) is a small molecule Bromodomain and Extra-Terminal motif (BET) inhibitor being studied in a Phase 1 clinical trial in patients with advanced hematologic malignancies and solid tumors. Mivebresib binds to BRD4 with a Ki of 1.5 nM. Comprehensive preclinical characterization of ABBV-075 demonstrated broad activity across cell lines and tumor models, representing a variety of hematologic malignancies and solid tumor indications. In most cancer cell lines derived from solid tumors, ABBV-075 triggers prominent G1 cell-cycle arrest without extensive apoptosis. Consistent with its broad spectrum of activities in vitro, ABBV-075 has comparable or superior efficacies to standard of care agents in flank xenograft mouse models of non-small-cell and small cell lung cancers, pancreatic, breast, prostate, head & neck cancers, multiple myeloma, diffuse large B cell lymphoma and leukemia.

CPI-0610 is a small molecule inhibitor of the Bromodomain and Extra-Terminal (BET) family of proteins, with potential antineoplastic activity. Upon administration, the BET inhibitor CPI-0610 binds to the acetylated lysine recognition motifs on the bromodomain of BET proteins, thereby preventing the interaction between the BET proteins and acetylated histone peptides. This disrupts chromatin remodeling and gene expression. Prevention of the expression of certain growth-promoting genes may lead to an inhibition of tumor cell growth. CPI-0610 is currently being evaluated in three Phase 1 clinical trials in the U.S.

Apabetalone (RVX-208) is a small molecule BET bromodomain inhibitor selective for BRD4-BD2 undergoing clinical development as a potential therapy to enhance ApoA-I production and treat atherosclerosis and prevent cardiovascular disease events. Apabetalone increases apolipoprotein A-I and high-density lipoprotein cholesterol (HDL-Cholesterol) in vitro and in vivo which is believed to provide a new approach to treating atherosclerosis through the stimulation of reverse cholesterol transport. RVX-208 increased the Tm of all BET bromodomains, indicative of binding. RVX-208 competes for acetylated histone H4 peptide binding to both bromodomains of BRD4, similar to JQ-1, but with a preference for BD2 over BD1. RVX-208 also binds to the bromodomains of BRDs 2 and 3 with a similar preference for BD2 (Kd~5–30 nM) over BD1 (Kd~2–3 uM). Treatment of humans for 1 week with oral RVX-208 increased apoA-I, pre-beta-HDL, and HDL functionality. Resverlogix Corp. has commenced a Phase 3 clinical trial in cardiovascular disease patients with type 2 diabetes mellitus with a primary endpoint of time to first occurrence of Major Adverse Cardiac Events (MACE).

I-BET-762 (GSK 525762) is a small molecule benzodiazepine, by 'mimicking' acetylated histones interferes with the recognition of acetylated histones by BET family of bromodomains (BRD2, BRD3, and BRD4), which disrupts chromatin remodeling and gene expression. Prevention of the expression of certain growth-promoting genes may lead to an inhibition of tumour cell growth. GlaxoSmithKline is developing GSK 525762 for the oral treatment of solid tumours and haematological malignancies.

(+)-JQ1 is a selective and potent inhibitor of Bromodomain and Extra-Terminal motif (BET) proteins. These are important epigenetic regulators facilitating the transcription of genes in chromatin areas linked to acetylated histones. (+)-JQ1 engages the bromodomain pocket in a manner that is competitive with acetylated peptide binding, thereby causing the displacement of BET proteins from chromatin. However, the inhibitor’s half life is only one hour, so it has short-lasting effects.