The present invention relates to a compound represented by formula (I 1) formula (I 2) or formula (I 3) having an antiviral effect or a pharmaceutically acceptable salt thereof and in further detail to a pyridone derivative having HIV integrase inhibiting activity and a drug particularly an anti HIV drug containing the derivative. The compound of the present invention has integrase inhibiting activity and/or cell propagation inhibiting activity against a virus particularly HIV or a resistant virus thereof. Thus the compound of the present invention is useful in the prevention or treatment of a variety of illnesses and viral infections (such as AIDS) in which integrase plays a role. (Each symbol in the formulas is as defined in the Specification.)
