The invention provides a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein: A is C1-6alkyl, C3-6cycloalkyl, —CH2—R6, —CHMe-R7, —CMe2-R7, or optionally substituted aryl; wherein, when A is optionally substituted aryl, said aryl group is optionally substituted with 1 to 3 substituents, which may be the same or different, selected from the group consisting of halogen, C1-6alkyl, —CF3, C1-4alkoxy, C1fluoroalkoxy, cyano, NR8R9, and pyridyl wherein the pyridyl is optionally substituted by one methyl; R1 is chlorine, fluorine, —CF3, cyano or C1-6alkyl; R2, R3 and R5 independently are hydrogen, fluorine, chlorine, —CF3, cyano or C1-6alkyl, such that at least one of R2, R3 and R5 is other than hydrogen; R4 is hydrogen. These compounds and salts are thought to be P2X7 receptor antagonists. The invention also provides for the treatment of pain, inflammation, rheumatoid arthritis, osteoarthritis, or a neurodegenerative disease.