Chemical proteomics identifies a novel off-target protein of small molecule NLRP3 inflammasome inhibitor MCC950

Inhibition of inflammasome and pyroptotic pathways are promising strategies for clinical treatment of autoimmune and inflammatory disorders. MCC950, a potent inhibitor of the NLR-family inflammasome pyrin domain-containing 3 (NLRP3) protein, has shown encouraging results in animal models for a range of conditions; however, little is known about its off-target effects. We have designed, synthesized and applied a novel photoaffinity alkyne-tagged probe for MCC950 which shows direct engagement with NLRP3 and inhibition of inflammasome activation in macrophages. Affinity-based chemical proteomics in live macrophages identified several potential off-targets, and independent cellular thermal proteomic profiling revealed stabilization of these by MCC950. This is the results of the affinity-based proteomics.