Discovery of Ibrutinib-based BTK PROTACs with in vivo anti-inflammatory efficacy by inhibiting NF-κB activation

As a critical upstream regulator of nuclear factor-κB (NF-κB) activation, Bruton's tyrosine kinase (BTK) has been identified to be an effective therapeutic target for the treatment of acute or chronic inflammatory diseases. Herein, we describe the design, synthesis and structure-activity-relationship analysis of a novel series of Ibrutinib-based BTK PROTACs by recruiting Cereblon (CRBN) ligase. Among them, compound 15 was identified as the most potent degrader with a DC50 of 3.18 nM, significantly better than the positive control MT802 (DC50 of 63.31 nM). Compound 15 could also degrade BTK protein in Lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and suppress the mRNA expression and secretion of proinflammatory cytokines such as IL-1β and IL-6 by inhibiting NF-κB activation. Furthermore, compound 15 reduced inflammatory responses in a mouse zymosan-induced peritonitis (ZIP) model. Our findings demonstrated for the first time that targeting BTK degradation by PROTACs might be an alternative option for the treatment of inflammatory disorders, and compound 15 represents one of the most efficient BTK PROTACs (DC50 = 3.18 nM; Dmax = 99.90%; near 100% degradation at 8 h) reported so far and could serve as a lead compound for further investigation as an anti-inflammatory agent.