A Probe for NLRP3 Inflammasome Inhibitor MCC950 Identifies Carbonic Anhydrase 2 as a Novel Target

[Image: see text] 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, until now, no off-targets have been identified. Herein, we report the design, synthesis, and application of a novel photoaffinity alkyne-tagged probe for MCC950 (IMP2070) 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, including carbonic anhydrase 2 (CA2) as a specific target of IMP2070, and independent cellular thermal proteomic profiling revealed stabilization of CA2 by MCC950. MCC950 displayed noncompetitive inhibition of CA2 activity, confirming carbonic anhydrase as an off-target class for this compound. These data highlight potential biological mechanisms through which MCC950 and derivatives may exhibit off-target effects in preclinical or clinical studies.