Discovery of Orally Bioavailable Chromone Derivatives as Potent and Selective BRD4 Inhibitors: Scaffold Hopping, Optimization, and Pharmacological Evaluation

Bromodomain-containing protein 4 (BRD4) represents a promising drug target for anti-inflammatory therapeutics. Herein, we report the design, synthesis, and pharmacological evaluation of novel chromone derivatives via scaffold hopping to discover a new class of orally bioavailable BRD4-selective inhibitors. Two potent BRD4 bromodomain 1 (BD1)-selective inhibitors 44 (ZL0513) and 45 (ZL0516) have been discovered with high binding affinity (IC50 values of 67-84 nM) and good selectivity over other BRD family proteins and distant BD-containing proteins. Both compounds significantly inhibited the expression of Toll-like receptor-induced inflammatory genes in vitro and airway inflammation in murine models. The cocrystal structure of 45 in complex with human BRD4 BD1 at a high resolution of 2.0 angstrom has been solved, offering a solid structural basis for its binding validation and further structure-based optimization. These BRD4 BD1 inhibitors demonstrated impressive in vivo efficacy and overall promising pharmacokinetic properties, indicating their therapeutic potential for the treatment of inflammatory diseases.