In the search for new NLRP3 inhibitors: chemical modulation of the 1-(piperidin-4-yl)-1,3-dihydro-2 Hbenzo[d]imidazole-2-one scaffold

The NLRP3 inflammasome is a cytosolic complex that plays a fundamental role in immune system activation. Different signals can lead to inflammasome activation. Once activated, NLRP3 undergoes a conformational change and then oligomerizes triggering the auto-proteolytic cleavage of pro-caspase-1 into the active caspase- 1. The activated caspase-1 can activate IL-1β, IL-18 and to cleave the protein gasdermin-D (GSDMD) involved in the pyroptotic cell death. In this study, we used a pharmacophore-hybridization strategy by combining the structure of the acrylic acid derivative INF39 with the 1-(piperidin-4-yl)1,3-dihydro-2H-benzo[d]imidazole-2-one substructure present in HS203873, a recently identified NLRP3 binder. A series of differently modulated benzo[d]imidazole-2-one derivatives were designed and synthesised from 2. The obtained compounds were screened in vitro to test their ability to inhibit NLRP3-dependent pyroptosis and IL-1β release in PMA-differentiated THP-1 cells stimulated with LPS/ATP. The selected compounds were evaluated for their ability to reduce the ATPase activity of human recombinant NLRP3 using a newly developed assay. Finally, computational simulations were applied for building the first complete model of the NLRP3 inactive state and for identifying possible binding sites available to the tested compounds. The analyses led us to suggest a mechanism of protein-ligand binding that might explain the activity of the compounds.