Targeting the NLRP3 inflammasome for inflammatory disease therapy

Abstract

The NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a megadalton complex implicated in numerous inflammation-driven diseases including COVID-19, Alzheimer's disease, and gout. Although past efforts have focused on inhibiting IL-1β downstream of NLRP3 activation using drugs such as canakinumab, no FDA-approved NLRP3-targeted inhibitors are currently available. MCC950, a direct NLRP3 inhibitor, showed promise but exhibited off-target effects. Recent research has focused on optimizing the sulfonylurea-based MCC950 scaffold by leveraging recent structural and medicinal chemistry insights into the NLRP3 nucleotide-binding and oligomerization (NACHT) domain to improve solubility and clinical efficacy. In addition, oxidized DNA (oxDNA) has emerged as a key inflammasome trigger, and molecules targeting the pyrin domain have shown promise in inhibiting NLRP3 activation. This review discusses the role of NLRP3 in inflammation-related diseases, the status of ongoing clinical trials, and emerging small-molecule therapeutics targeting NLRP3.

Keywords: NLRP3 inflammasome; ROS; SU0268; TH5487; mtDNA.

Figure 1.. Mechanisms of NLRP3 inflammasome activation and inhibition.

In priming, lipopolysaccharide (LPS) or IL-1β activates NF-κB and induces the expression of proinflammatory cytokines and NLRP3. Activation mediated by ATP, nigericin, and particulate matter causes ion fluxes, mitochondrial dysfunction, reactive oxygen species (ROS) generation, and DNA damage. NLRP3 binds to oxidized mitochondrial DNA (ox-mtDNA) released through the mitochondrial permeability transition pore (mPTP), leading to inflammasome assembly. Inhibition mechanisms are shown for drugs that prevent NLRP3 activation or inflammasome formation (red boxes). Abbreviations: CARD, caspase activation and recruitment domain; LRR, leucine-rich repeat domain; MCU, mitochondrial calcium uniporter; MSU, monosodium urate; NACHT, nucleotide-binding and oligomerization domain.

Figure 2.. Structures of the NLRP3 nucleotide-binding and oligomerization (NACHT) active site bound to small molecules.

In each structure the color scheme for the NACHT subdomains is the same: nucleotide-binding domain (NBD) residues 131–373 are shown in purple, helical domain 1 (HD1) residues 374–434 (green), winged-helix domain (WHD) residues 435–538 (pink), and helical domain 2 (HD2) residues 539–676 (orange). (A) NP3-562 bound to the NLRP3 NACHT domain [44] (PDB: 8RI2). (B) NP3-146 bound to the NLRP3 NACHT domain [7] (PDB: 7ALV). (C) SN3-1 bound to the NLRP3 NACHT domain [45] (PDB: 8ZEM). (D) MCC950 bound to the NLRP3 NACHT domain [6] (PDB: 7PZC). (E) GDC-2394 bound to the NLRP3 NACHT domain [8] (PDB: 8ETR). (F) Compound 32 bound to the NLRP3 NACHT domain [47] (PDB: 8WSM). The ligand binds to the same active site across all structures. Images were rendered and constructed using University of California San Francisco (UCSF) ChimeraX [106].

Figure 3.. NLRP3 drug structures and their shared features.

NLRP3 inhibitors share a similar backbone and have many similar functional groups, including tricyclic ring systems (blue), sulfonylurea groups (green), hydroxyls (red), amides (gray), halogens (orange), urea (yellow), and sulfonyl groups (dark gray). TH5487 and SU0268 bind directly to the pyrin domain of NLRP3. TH5487 contains a 8-oxo-dG-like moiety.