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.)
