NLRP3-IN-9 (INF-4E) is a covalent NLRP3 ATPase inhibitor that blocks caspase-1 activation. It suppresses ATP- and nigericin-induced pyroptosis in human THP-1 cells in a time- and concentration-dependent manner. This inhibitor is a valuable tool for studying NLRP3 inflammasome biology in cellular models of inflammatory diseases.