The NLRP3 inflammasome is an intracellular oligomer regulating the activation of caspase-1 for the processing and secretion of IL-1β and IL-18. Although there is growing evidence to substantiate inflammasome inhibition as a therapeutic option for the treatment of inflammatory diseases, to date, there are no approved humans agents. Dapansutrile (OLT1177), an orally active β-sulfonyl nitrile molecule, inhibits activation of the NLRP3 inflammasome.
In vitro, nanomolar concentrations of Dapansutrile reduced IL-1β and IL-18 release following canonical and noncanonical NLRP3 inflammasome activation. The molecule showed no effect on the NLRC4 and AIM2 inflammasomes, suggesting specificity for NLRP3. In LPS-stimulated human blood-derived macrophages, Dapansutrile decreased IL-1β levels by 60% and IL-18 by 70% at concentrations 100-fold lower in vitro than plasma concentrations safely reached in humans.
In addition, the inhibitor also reduced IL-1β release and caspase-1 activity in freshly obtained human blood neutrophils. In monocytes isolated from patients with cryopyrin-associated periodic syndrome (CAPS), it inhibited LPS-induced IL-1β release by 84% and 36%. Immunoprecipitation and FRET analysis demonstrated that Dapansutrile prevented NLRP3-ASC, as well as NLRP3-caspase-1 interaction, thus inhibiting NLRP3 inflammasome oligomerization. In a cell-free assay, Dapansutrile reduced ATPase activity of recombinant NLRP3, suggesting direct targeting of NLRP3. Mechanistically, Dapansutrile did not affect potassium efflux, gene expression, or synthesis of the IL-1β precursor. Steady-state levels of phosphorylated NF-κB and IkB kinase were significantly lowered in spleen cells from Dapansutrile-treated mice.
Dapansutrile is a specific inhibitor of the NLRP3 inflammasome, with no effect on the NLRC4 and AIM2 inflammasomes. It promotes mitochondrial metabolism in a tissue with high energy demands while preventing the accumulation of proinflammatory succinate.