Compounds useful as inhibitors of inflammasome activity (I) A compound of formula (I) or pharmaceutically acceptable salt thereof is provided, wherein R1 is a 5 or 6 membered alkyl or aryl monocycle, having at least one group substituent comprising a (2-8C) alkyl, or a 9 or 10 membered bicyclic partially unsaturated carbocyclic ring system which may be optionally substituted as herein defined, or a 12, 13, 14, 15 or 16 membered tricyclic partially unsaturated carbocyclic ring system as herein defined; R2 is H; R3 is H or alkyl(C1-4)-R7 where R7 is a substituent as herein defined; and R4 is H, alkyl, monocyclic alkyl or monocyclic aryl group. The compounds defined herein inhibit the maturation of cytokines of the IL-1 family by inhibiting inflammasome and may be useful in the treatment of disorders in which inflammasome activity is implicated, such as inter alia autoinflammatory and autoimmune diseases and cancer.