The invention provides compounds of the formula (6): or a salt, N-oxide or tautomer thereof, wherein A is CH, CF or nitrogen; E is CH, CF or nitrogen; and R0 is hydrogen or C1-2 alkyl; R1a is selected from CONH2; CO2H; an optionally substituted acyclic C1-8 hydrocarbon group; and an optionally substituted monocyclic carbocyclic or heterocyclic group of 3 to 7 ring members, of which 0, 1, 2, 3 or 4 are heteroatom ring members selected from O, N and S; R2 is selected from hydrogen and a group R2a; R2a is selected from an optionally substituted acyclic C1-8 hydrocarbon group; an optionally substituted monocyclic carbocyclic or heterocyclic group of 3 to 7 ring members, of which 0, 1 or 2 ring members are heteroatom ring members selected from O, N and S; and an optionally substituted bicyclic heterocyclic group of 9 or 10 ring members, of which 1 or 2 ring members are nitrogen atoms; wherein at least one of R1 and R2 is other than hydrogen; R3 is an optionally substituted 3- to 10-membered monocyclic or bicyclic carbocyclic or heterocyclic ring containing 0, 1, 2 or 3 heteroatom ring members selected from N, O and S; R4a is selected from halogen; cyano; C1-4 alkyl optionally substituted with one or more fluorine atoms; C1-4 alkoxy optionally substituted with one or more fluorine atoms; hydroxy-C1-4 alkyl; and C1-2 alkoxy-C1-4 alkyl; R5 is selected from hydrogen and a substituent R5a; and R5a is selected from C1-2 alkyl optionally substituted with one or more fluorine atoms; C1-3 alkoxy optionally substituted with one or more fluorine atoms; halogen; cyclopropyl; cyano; and amino. The compounds have activity against hepatitis C virus and can be used in the prevention or treatment of hepatitis C viral infections.