Discovery of Potent, Specific, and Orally Available NLRP3 Inflammasome Inhibitors Based on Pyridazine Scaffolds for the Treatment of Septic Shock and Peritonitis

The NLRP3 inflammasome is a multiprotein complex that is a component of the innate immune system, involved in the production of pro-inflammatory cytokines. Its abnormal activation is associated with many inflammatory diseases. In this study, we designed and synthesized a series of NLRP3 inflammasome inhibitors based on pyridazine scaffolds. Among them, <b>P33</b> exhibited significant inhibitory effects against nigericin-induced IL-1β release in THP-1 cells, BMDMs, and PBMCs, with IC₅₀ values of 2.7, 15.3, and 2.9 nM, respectively. Mechanism studies indicated that <b>P33</b> directly binds to NLRP3 protein (<i>K</i>_D = 17.5 nM), inhibiting NLRP3 inflammasome activation and pyroptosis by suppressing ASC oligomerization during NLRP3 assembly. Additionally, <b>P33</b> displayed excellent pharmacokinetic properties, with an oral bioavailability of 62%. <i>In vivo</i> efficacy studies revealed that <b>P33</b> significantly ameliorated LPS-induced septic shock and MSU crystal-induced peritonitis in mice. These results indicate that <b>P33</b> has great potential for further development as a candidate for treating NLRP3 inflammasome-mediated diseases.