The present invention provides a compound of Formula (IA) or a pharmaceutically acceptable salt thereof: wherein R1 represents C1-4 alkyl, C2-6 alkenyl, C2-6 alkynyl, C3-6 cycloalkyl, C3-6 cycloalkylmethyl-, phenyl-X&mdash； or heteroaryl, any of which may be optionally substituted； X represents &mdash；(CR12R13)n&mdash；； n represents 0 to 2； and R7, R8, R9, R10 and R11 independently represent H, halogen, or cyano； or optionally substituted C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl or C3-6 cycloalkyl； such that at least two of R7, R8, R9, R10 and R11 represent a group other than H and at least one of R7 and R11 represents a group other than H； and wherein the compound is other than N-[(2,4-dichlorophenyl)methyl]5-oxo-1-(phenylmethyl)-3-pyrrolidinecarboxamide. The compounds and salts are thought to modulate P2X7 receptor function and be capable of antagonizing the effects of ATP at the P2X7 receptor.
