Oxazol/thiazol-derivatives activators of the hppar-alpha receptor

A compound of formula (I) and pharmaceutically acceptable salts, solvates and hydrolysable esters thereof Wherein X1 represents O or S; R and R are independently H or C1-3 alkyl or R and R which are bonded to the same carbon atom may together with the carbon atom to which they are bonded form a 3-5 membered cycloalkyl ring; R and R independently represent H, halogen, -CH3 and -OCH3; R represents H or C1-6 alkyl X2 represents NH, NCH3 or O; One of Y and Z is N, and the other is O or S; R represents phenyl or pyridyl (wherein the N is in position 2 or 3) and is optionally substituted by one or more halogen, CF3, C1-6 straight or branched alkyl (optionally substituted by halogen), with the provision that when R is pyridyl, the N is unsubstituted.