A compound of formula (I) ** Formula ** wherein X1, X2 and X3 are each independently selected from the group consisting of H, F, Cl, Br, I, -OT1, - N (T2) (T3 ), -NHC (>； = O) T4, nitro, cyano, cyclopropyl and -C1-3 alkyl, with the proviso that at least two substituents selected from X1, X2 and X3 are each independently selected from the group consisting of F, Cl, Br and I； Z1 and Z2 are each independently selected from the group consisting of H, -C1-6 alkyl, -OT1 and -N (T2) (T3)； Z3 and Z4 are taken together to form an oxo group on the carbon atom to which they are attached； or Z3 and Z4 are each independently selected from the group consisting of H, -C1-6 alkyl, -OT1 and -N (T2) (T3)； Z5 and Z6 are taken together to form an oxo group on the carbon atom to which they are attached； or Z5 and Z6 are each independently selected from the group consisting of H, -C1-6 alkyl, -OT1 and -N (T2) (T3)； X4 is absent or is selected from the group consisting of -NR4-, -N (R4) (CH2) -, -C (>； = O) NH- and -C (>； = O) -； R4 is selected from H and -C 1-6 alkyl； Y1 is selected from the group consisting of H, -C 1-6 alkyl and a saturated or unsaturated aromatic carbocycle or heterocycle of 4 to 7 members, with the proviso that the point of attachment in said heterocycle is carbon if X4 is -NR4- or -C (>； = O) NH-, wherein said -C1-6 alkyl is optionally substituted with one or more substituents independently selected from -OT1, -ST1, -N (T2) (T3) and a saturated heterocycle of 5 to 6 members, and wherein said saturated or unsaturated aromatic carbocycle or heterocycle of 4 to 7 members is optionally substituted with one or more substituents independently selected from F, Cl, Br, I, -C (>； = O) H, -OT1 , -N (T2) (T3), -C (>； = O) N (T2) (T3), -C (>； = O) OT1, - ST1 and -C1-3 alkyl, wherein said -C1 alkyl 3 is optionally substituted with one or more substituents independently selected from -OT1 and -N (T2) (T3)； T1, T2 and T3 are each independently selected from H and -C
