Substituted thiazolidinedione derivatives

Compounds of formula (I): or a tautomeric form thereof, or a pharmaceutically acceptable salt thereof, or a pharmaceutically acceptable solvate thereof, wherein: A represents a substituted or unsubstituted aromatic heterocyclyl group; R represents a hydrogen atom, an alkyl group, an acyl group, an aralkyl group, wherein the aryl moiety may be substituted or unsubstituted, or a substituted or unsubstituted aryl group; R and R each represent hydrogen, or R and R together represent a bond; A represents a benzene ring having in total up to five substituents; and n represents an integer in the range of from 2 to 6; pharmaceutical compositions containing such compounds and the use of such compounds and compositions in medicine.