This invention concerns a compound of formula a N-oxide, a pharmaceutically acceptable addition salt, a quaternary amine and a stereochemically isomeric form thereof, wherein ring A represents a 6-membered heterocycle; R1 is hydrogen; aryl; formyl; C1-6alkylcarbonyl; optionally substituted C1-6alkyl; C1-6alkyloxycarbonyl; optionally substituted C1-6alkyloxyC1-6alkylcarbonyl; X is a direct bond or a linker atom or group; Z is O or S; R2 is hydrogen, C1-10alkyl, C2-10alkenyl, C2-10alkynyl, a carbocycle or a heterocycle, each of said groups may optionally be substituted; R3 is hydrogen; hydroxy; halo; optionally substituted C1-6alkyl or C2-6alkenyl or C2-6alkynyl; C1-6alkyloxy; C1-6alkylthio; C1-6alkyloxycarbonyl; C1-6alkylcarbonyloxy; carboxyl; cyano; nitro; amino; mono- or di(C1-6alkyl)amino; polyhaloC1-6alkyl; polyhaloC1-6alkyloxy; polyhaloC1-6alkylthio; R21; R21—C1-6alkyl; R21—O—; R21—S—; R21—C(═O)—; R21—S(═O)p—; R7—S(═O)p—; R7—S(═O)p—NH—; R21—S(═O)p—NH—; R7—C(═O)—; —NHC(═O)H; —C(═O)NHNH2; R7—C(═O)—NH—; R21—C(═O)—NH—; —C(═NH)R7; —C(═NH)R21; R4a or R4b each independently represent hydrogen, R8, —Y1—NR9—Y2—NR10R11, —Y1—NR9—Y1—R8, —Y1—NR9R10; provided that —X—R2 and/or R3 is other than hydrogen; their use, pharmaceutical compositions comprising them and processes for their preparation.