Thiazolidinedione derivatives

A compound of formula (I):

• ##STR23## or a tautomeric form thereof and/or a pharmaceutically acceptable salt thereof, and/or a pharmaceutically acceptable solvate thereof, wherein:
• R.sup.1 and R.sup.2 each independently represent an alkyl group, a substituted or unsubstituted aryl group or an aralkyl group being substituted or unsubstituted in the aryl or alkyl moiety;
• or R.sup.1 together with R.sup.2 represents a linking group, the linking group consisting of an optionally substituted methylene group and either a further optionally substituted methylene group or an O or S atom, optional substituents for the said methylene groups being selected from alkyl, aryl or aralkyl or substituents of adjacent methylene groups together with the carbon atoms to which they are attached form a substituted or unsubstituted phenylene group;
• R.sup.3 and R.sup.4 each represent hydrogen, or R.sup.3 and R.sup.4 together represent a bond;
• A.sup.1 represents a benzene ring having in total up to three optional substituents;
• X represents O or S;
• and
• n represents an integer in the range of from 2 to 6.