A compound of formula: 1 R is selected from an optionally substituted aryl, heteroaryl, carbocyclyl and heterocyclyl group, the optional substitution being with one or more substituents selected from halo, CN, NO 2, R 3, OR 3, N(R 3) 2, COR 3, CO 2 R 3, C(=O)SR 3, SR 3, S(=O)R 3, SO 2 R 3, NR 4 C(=O)R 3, NR 4 CO 2 R 3, OC(=O)NR 3 R 4, NR 4 SO 2 R 3, C(=NR 4)NR 3 R 4, C(=S)NR 3 R 4, NR 4 C(=NR 4)NR 3 R 4, NR 4 C(=S)NR 3 R 4, NR 4 C(=O)NR 3 R 4, CONR 3 R 4 and SO 2 NR 3 R 4; 2 R is an optionally substituted aromatic 8-14 membered fused bicyclic or tricyclic ring system in which one or more of the carbon atoms may be replaced by N, O, S, SO or SO 2 and the optional substitution being with one or more substituents selected from halo, CN, NO 2, R 3, OR 3, N(R 3) 2, COR 3, CO 2 R 3, C(=O)SR 3, SR 3, S(=O)R 3, SO 2 R 3, NR 4 C(=O)R 3, NR 4 CO 2 R 3, OC(=O)NR 3 R 4, NR 4 SO 2 R 3, C(=NR 4)NR 3 R 4, C(=S)NR 3 R 4, NR 4 C(=NR 4)NR 3 R 4, NR 4 C(=S)NR 3 R 4, NR 4 C(=O)NR 3 R 4, CONR 3 R 4 and SO 2 NR 3 R 4; 3 R is selected from H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 7 carbocyclyl, C 4 -C 7 heterocyclyl and 5- or 6- membered aryl or heteroaryl, any of which may be optionally substituted with one or more substituents selected from halo, CN, NO 2, R 4, OR 4, N(R 4) 2, COR 4, CO 2 R 4, C(=O)SR 4, SR 4, S(=O)R 4, SO 2 R 4, NR 4 C(=O)R 4, NR 4 CO 2 R 4, OC(=O)NR 4) 2, NR 4 SO 2 R 4, C(=NR 4)N(R 4) 2, C(=S)N(R 4) 2, NR 4 C(=NR 4)N(R 4) 2, NR 4 C(=S)N(R 4) 2, NR 4 C(=O)N(R 4) 2, CON(R 4) 2 and SO 2 N(R 4) 2; 4 R is selected from hydrogen, C 1 -C 6 alkyl and C 3 -C 7 carbocyclyl, optionally substituted with one or more halo atoms; or a pharmaceutically acceptable N-oxide, salt, hydrate or solvate thereof, for use in a method for the treatment of Clostridium difficile- associated disease (CDAD). R is selected from an optionally substituted aryl, heteroaryl, carbocyclyl and heterocyclyl group, the optional substitution being with one or more substituents selected from halo, CN, NO 2, R 3, OR 3, N(R 3) 2, COR 3, CO 2 R 3, C(=O)SR 3, SR 3, S(=O)R 3, SO 2 R 3, NR 4 C(=O)R 3, NR 4 CO 2 R 3, OC(=O)NR 3 R 4, NR 4 SO 2 R 3, C(=NR 4)NR 3 R 4, C(=S)NR 3 R 4, NR 4 C(=NR 4)NR 3 R 4, NR 4 C(=S)NR 3 R 4, NR 4 C(=O)NR 3 R 4, CONR 3 R 4 and SO 2 NR 3 R 4; 2 R is an optionally substituted aromatic 8-14 membered fused bicyclic or tricyclic ring system in which one or more of the carbon atoms may be replaced by N, O, S, SO or SO 2 and the optional substitution being with one or more substituents selected from halo, CN, NO 2, R 3, OR 3, N(R 3) 2, COR 3, CO 2 R 3, C(=O)SR 3, SR 3, S(=O)R 3, SO 2 R 3, NR 4 C(=O)R 3, NR 4 CO 2 R 3, OC(=O)NR 3 R 4, NR 4 SO 2 R 3, C(=NR 4)NR 3 R 4, C(=S)NR 3 R 4, NR 4 C(=NR 4)NR 3 R 4, NR 4 C(=S)NR 3 R 4, NR 4 C(=O)NR 3 R 4, CONR 3 R 4 and SO 2 NR 3 R 4; 3 R is selected from H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, C 3 -C 7 carbocyclyl, C 4 -C 7 heterocyclyl and 5- or 6- membered aryl or heteroaryl, any of which may be optionally substituted with one or more substituents selected from halo, CN, NO 2, R 4, OR 4, N(R 4) 2, COR 4, CO 2 R 4, C(=O)SR 4, SR 4, S(=O)R 4, SO 2 R 4, NR 4 C(=O)R 4, NR 4 CO 2 R 4, OC(=O)NR 4) 2, NR 4 SO 2 R 4, C(=NR 4)N(R 4) 2, C(=S)N(R 4) 2, NR 4 C(=NR 4)N(R 4) 2, NR 4 C(=S)N(R 4) 2, NR 4 C(=O)N(R 4) 2, CON(R 4) 2 and SO 2 N(R 4) 2; 4 R is selected from hydrogen, C 1 -C 6 alkyl and C 3 -C 7 carbocyclyl, optionally substituted with one or more halo atoms;