A heterocyclic compound of the formula (I): wherein B1 is —C(R2)═ or —N═; R1′ is H, etc.; one of R1 and R2 is -Z1-Z2-Z3-R5 wherein Z1 and Z3 are independently single bond, optionally substituted alkylene, etc.; Z2 is single bond, optionally substituted alkylene, etc.; R1 is optionally substituted aryl, optionally substituted heteroaryl, etc., and the other of R1 and R2 is H; -A1- is —C(—Y)═C(—RA)—C(—R3)═C(—R4)—, etc. wherein Y is OH, etc.; RA is —COR7 wherein R7 is OH, etc.; one of R3 and R4 is carboxy, etc., and the other of R1 and R2 is H, etc, a prodrug thereof, a pharmaceutically acceptable salt thereof, and a solvate thereof, having an antiviral activity, more particularly, an inhibitory activity against HIV integrase, and a pharmaceutical composition containing the same, especially an anti-HIV drug.