Potent and selective bivalent inhibitors of BET bromodomains

Abstract

Proteins of the bromodomain and extraterminal (BET) family, in particular bromodomain-containing protein 4 (BRD4), are of great interest as biological targets. BET proteins contain two separate bromodomains, and existing inhibitors bind to them monovalently. Here we describe the discovery and characterization of probe compound biBET, capable of engaging both bromodomains simultaneously in a bivalent, in cis binding mode. The evidence provided here was obtained in a variety of biophysical and cellular experiments. The bivalent binding results in very high cellular potency for BRD4 binding and pharmacological responses such as disruption of BRD4-mediator complex subunit 1 foci with an EC of 100 pM. These compounds will be of considerable utility as BET/BRD4 chemical probes. This work illustrates a novel concept in ligand design-simultaneous targeting of two separate domains with a drug-like small molecule-providing precedent for a potentially more effective paradigm for developing ligands for other multi-domain proteins.

Selective BET bromodomain inhibition as an antifungal therapeutic strategy

“…Such inhibition could be achieved via a single compound, which targets both BDs or through the combined use of two compounds, supplied independently or covalently linked as a bivalent BD inhibitor. Indeed, dual-warhead BET inhibitors that simultaneously engage both BDs within a single BET protein have recently been described, which possess greatly enhanced biochemical and cellular potency as well as increased efficacy in animal disease models relative to monovalent inhibitors474849. Alternatively, one could envisage a Proteolysis Targeting Chimera approach, whereby a single BD inhibitor conjugated to a ligand for an E3 ubiquitin ligase would trigger the degradation of Ca Bdf1, as recently demonstrated for human BET proteins50515253.…”

Targeting Mechanotransduction at the Transcriptional Level: YAP and BRD4 Are Novel Therapeutic Targets for the Reversal of Liver Fibrosis

“…In the context of fibrosis, inhibiting BRD4 with JQ1 inhibits both lung and liver fibrosis as well as HSC activation in murine models, including reducing TGF-β-mediated Col1A1 expression and extracellular matrix remodeling (Tang et al, 2013; Ding et al, 2015). Thus, JQ1 represents an attractive small molecule for further study as potential treatment of human fibroproliferative diseases and the future development of more specific and stable BRD4 inhibitors (Theodoulou et al, 2016; Waring et al, 2016) may open new opportunities for anti-fibrotic therapy.…”

Development and Validation of 2D Difference Intensity Analysis for Chemical Library Screening by Protein‐Detected NMR Spectroscopy

“…We further validated our approach against the second bromodomain of BRD4, BRD4(BD2), an epigenetic regulatory protein of the bromodomain and extraterminal domain (BET) family (BRDT, BRD2, BRD3, and BRD4) implicated in the progression of various forms of cancer and inflammatory disease . BET family proteins localize to the nucleus and specifically recognize and bind to acetylated lysine residues, influencing transcription by marking sites of acetylated chromatin throughout the genome .…”

“…BET family proteins localize to the nucleus and specifically recognize and bind to acetylated lysine residues, influencing transcription by marking sites of acetylated chromatin throughout the genome . Currently, small molecule inhibitors of BET bromodomains, which selectively displace BET proteins from acetylated histones, are in clinical trials for applications that include hematological malignancies, solid tumors, and inflammatory disorders . However, these potential drugs are nonselective, as they bind all four BET family proteins with equal low nanomolar affinity .…”