The invention provides compounds that are useful in the treatment of hepatitis C virus (HCV) infections. The compounds have the formula (1): or a salt, N-oxide, tautomer or stereoisomer thereof, wherein A is CH or N; E is CH or N; R1 is selected from: an optionally substituted acyclic C1-8 hydrocarbon group wherein one carbon atom of the acyclic C1-8 hydrocarbon group may optionally be replaced by O, S, NRc, S(O) or SO2, or two adjacent carbon atoms of the acyclic C1-8 hydrocarbon group may optionally be replaced by CONRc, NRcCO, NRcSO2 or SO2NRc provided that in each case at least one carbon atom of the acyclic C1-8 hydrocarbon group remains; 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 hydrogen or X—R8; X is a C1-8 alkanediyl group wherein one carbon atom of the C1-8 alkanediyl group may optionally be bonded to a —CH2—CH2— moiety to form a cyclopropane-1,1-diyl group or two adjacent carbon atoms of the C1-8 alkanediyl group may optionally be bonded to a —(CH2)n moiety, where n is 1 to 5, to form a C3-7-cycloalkane-1,2-diyl group; R3 is an optionally substituted 3- to 10-membered monocyclic or bicyclic carbocyclic or heterocyclic ring containing 0-3 heteroatom ring members selected from N, O and S; R4 is hydrogen or R4a wherein R4a is halogen; cyano; C1-4 alkyl; fluoro-1-4 alkyl; C1-4 alkoxy; fluoro-C1-4 alkoxy; hydroxy-C1-4 alkyl; or C1-2 alkoxy-C1-4 alkyl; R5 is hydrogen or R5a wherein R5a is selected from C1-2 alkyl optionally substituted with fluorine; C1-3 alkoxy optionally substituted with fluorine; halogen; cyclopropyl; and cyano; R8 is hydroxy or C(═O)NR10R11; provided that when R8 is hydroxy, there are at least two carbon atoms in line between the hydroxy group and the nitrogen atom to which X is attached; R10 is hydrogen or C1-4 alkyl; and R11 is hydrogen; amino-C2-4 alkyl or hydroxy-C2-4 alkyl; but excluding the compounds 1-(3-benzoylphenyl)-ethylamine and 1-(3-furan-2-oylcarbonylphenyl)-ethylamine.