Objective

Fragment-based approaches have been applied successfully to the discovery and optimization of ligands for a wide range of targets. Fragment-based lead discovery (FBLD) is proving particularly valuable for bromodomain (BRD)-containing proteins, an emerging family of epigenetic regulators with potential as targets for cancer, inflammation and multiple sclerosis. These proteins are able to recognize and read the acetylated lysine (KAc) modifications on histones and are subsequently responsible for transducing and translating signals into various normal or abnormal phenotypes. There are several BRD isoforms and compounds selective for individual BRDs would be useful pharmacological tools, with the potential to be therapeutic leads as well.  Sygnature’s fragment library was screened by surface plasmon resonance (SPR) to generate an initial set of hits against BRD3. These hits were then confirmed orthogonally by ligand-observed nuclear magnetic resonance (NMR), using saturation transfer difference (STD) experiments. Additional characterisation was undertaken by isothermal titration calorimetry (ITC), microscale thermophoresis (MST) and protein X-ray crystallography, identifying fragments that bind at the acetyl-lysine binding site of the first bromodomain in BRD3. Further chemical elaboration of these fragments could lead to a BRD3 specific molecule that could be utilized as a probe for elucidating the individual roles of the members of the BET-family.