Pyridone derivative

A compound of formula (I):

• wherein:
• R1 and R2 are the same or different and are each independently selected from:
• hydrogen, optionally substituted lower alkyl, optionally substituted lower cycloalkyl, optionally substituted lower alkylcarbonyl, optionally substituted lower alkyloxycarbonyl and optionally substituted lower alkylsulfonyl;
• or R1 and R2 form an optionally substituted aliphatic nitrogen-containing heterocyclic group together with the nitrogen atom to which they bind;
• X1, X2 and X3 are the same or different and are each independently selected from:
• unsubstituted methine and nitrogen atom, provided not all of X1, X2 and X3 simultaneously stand for nitrogen;
• X4, X5, X6 and X7 are the same or different and are each independently selected from:
• optionally substituted methine and nitrogen, provided that three or more of X4, X5, X6 and X7 are not simultaneously nitrogen;
• Y1 is selected from:
• a single bond, —O—, —NR—, —S—, —SO—, and —SO2—;
• Y2 is selected from:
• optionally substituted lower alkylene, optionally substituted lower alkenylene, and optionally substituted lower cycloalkylene;
• Y3 is selected from:
• a single bond, —O—, —NR—, —S—, —SO—, and —SO2—;
• R is selected from:
• hydrogen and optionally substituted lower alkyl;
• L is optionally substituted methylene;
• Z1 and Z2 are the same or different and are each independently selected from:
• a single bond and optionally substituted lower alkylene;
• or
• R1, L and Z2 together form an optionally substituted aliphatic nitrogen-containing heterocyclic group with the nitrogen to which R1 binds;
• and
• Ar stands for an optionally substituted aromatic carbocyclic group, optionally substituted heteroaromatic group or optionally substituted aliphatic carbocyclic group;
• or a pharmaceutically acceptable salt thereof.