The present invention relates to compounds of formula (I), tautomers, stereoisomers, pharmaceutically acceptable salts and pro-drugs thereof, to processes for their preparation, to pharmaceutical compositions containing such compounds and to their use in therapy wherein a dashed line indicates an optional bond； X represents: a 5- or 6-membered, unsaturated heterocyclic group optionally substituted by one or more (e.g. 1, 2 or 3) substituents independently selected from halogen (i.e. F, C1, Br, I), C1-6 alkyl (e.g. C1-3 alkyl), C1-6 haloalkyl (e.g. C1-3 haloalkyl), C1-6 alkoxy (e.g. C1-3 alkoxy), -CN, -NO2, -N(R)2, and -SO2R (where each R is independently H or C1-6 alkyl, e.g. H or C1-3 alkyl)； a C3-5 cycloalkyl group optionally substituted by one or more (e.g. 1 or 2) substituents independently selected from C1-6 alkyl (preferably C1-3 alkyl), C1-6 haloalkyl (e.g. C1-3 haloalkyl), and C1-6 alkoxy (e.g. C1-3 alkoxy)； or an aryl group optionally substituted by one or more (e.g. 1, 2 or 3) substituents independently selected from halogen (i.e. F, C1, Br, I), C1-6 alkyl (e.g C1-3 alkyl), C1-6 haloalkyl (e.g. C1-3 haloalkyl), and C1-6 alkoxy (e.g. C1-3 alkoxy)； Y represents: an aryl or heteroaryl group optionally substituted by one or more (e.g. 1, 2 or 3) substituents independently selected from halogen (i.e. F, Cl, Br, I), C1-6 alkyl (e.g C1-3 alkyl), C1-6 haloalkyl (e.g. C1-3 haloalkyl), and C1-6 alkoxy (e.g. C1-3 alkoxy)； a 5- or 6-membered, saturated heterocyclic group optionally substituted by one or more (e.g. 1, 2 or 3) substituents independently selected from C1-6 alkyl (preferably C1-3 alkyl), C1-6 haloalkyl (e.g. C1-3 haloalkyl), and C1-6 alkoxy (e.g. C1-3 alkoxy)； or a C3-6 cycloalkyl group optionally substituted by one or more (e.g. 1 or 2) substituents independently selected from C1-6 alkyl (preferably C1-3 alkyl), C1-6 haloalkyl (e.g. C1-3 haloalkyl), and C1-6 alkoxy (e.g. C1-3 alkoxy)； and Z represents: an aryl group optionally substituted by one or more
