Orally Bioavailable BRD4 BD1 Inhibitor ZL0516 Effectively Suppresses Colonic Inflammation in Animal Models of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), a chronic, progressive, and recurrent gastrointestinal inflammatory disorder, poses a significant threat to global health and exerts an adverse effect on the quality of life. Currently, there is a lack of effective therapies for IBD. Developing novel targeted therapies for IBD, particularly orally effective therapeutics, is a vital need for IBD patients. Herein, we first demonstrate that BRD4/NF-κB signaling is aberrantly activated in the colons of human IBD biopsy samples compared to that of normal healthy controls. ZL0516, a potent, selective, and orally bioavailable BRD4 BD1 inhibitor, significantly inhibits the TNFα- and LPS-induced expression of inflammatory cytokines in human colonic epithelial cells (HCECs) and peripheral blood mononuclear cells (PBMCs) with low cytotoxicity. Intriguingly, when administered in a preventive mode, ZL0516 significantly blocks dextran sulfate sodium (DSS)-induced murine colitis. When used in a therapeutic mode, ZL0516 effectively suppresses colonic inflammation in several IBD-relevant animal models: DSS-, oxazolone (OXA)-, and flagellin (Cbir1) T cell-induced chronic murine colitis models of IBD. ZL0516 suppresses IBD inflammatory responses in vitro and in vivo by blocking the activation of the BRD4/NF-κB signaling pathway. Also, we found that RVX208, a selective BRD4 BD2 inhibitor in Phase III clinical development, only displayed marginal effects in these IBD animal models. Collectively, our results demonstrate that specific BRD4 BD1 inhibition is a novel therapeutic strategy for IBD-associated colonic inflammation, and orally effective inhibitor ZL0516 is a promising candidate for the development of a novel therapeutic regimen against IBD.