A compound of formula wherein X 1, X 2, X 3 and X 4 are all CH or one of X 1, X 2, X 3 and X 4 is N and the others are CH; p is zero or an integer from 1 to 4; each R, when present, is in each occurrence independently selected from (C 1 -C 6)alkyl and halogen selected from F, Cl, Br and I; wherein preferably R is F, Cl or methyl; R 1 is pyrimidinyl, preferably pyrimidin-4yl, substituted by one or more group selected from -(CH 2) m NH 2; particularly preferably R 1 is 2-aminopyrimidin-4-yl; L is -C NH- or -NHC -; n is in each occurrence independently 0 or an integer selected from 1, 2 or 3; R 2 and R 3 are in each occurrence independently selected from the group consisting of -H, halogen, -OH, -(CH 2) m NR 4 R 5, (C 1 -C 6)alkyl, (C 1 -C 6)hydroxyalkyl, (C 1 -C 6) alkoxy, (C 1 -C 6) alkoxy (C 1 -C 6)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)haloalkoxy, (C 1 -C 6)haloalkoxy (C 1 -C 6)alkyl, (C 3 -C 10)cycloalkyl, aryl and (C 3 -C 6)heterocycloalkyl, each of which cycloalkyl, aryl and heterocycloalkyl is in its turn optionally and independently substituted with one or more groups selected from halogen, -OH, (C 1 -C 6)alkyl, (C 1 -C 6)hydroxyalkyl, (C 1 -C 6) alkoxy, (C 1 -C 6) alkoxy (C 1 -C 6)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)haloalkoxy, -(CH 2) m NR 4 R 5, -O-(CH 2) m NR 4 R 5, alkanoyl, aryl, heteroaryl, cycloalkyl, aryl-(C 1 -C 6)alkyl, heteroaryl-(C 1 -C 6)alkyl, (C 3 -C 8)heterocycloalkyl, (C 3 -C 8)heterocycloalkyl-(C 1 -C 6)alkyl, (C 3 -C 8)cycloalkyl-(C 1 -C 6)alkyl, each of said aryl, heteroaryl, cycloalkyl, heterocycloalkyl is still further optionally substituted by one or more group selected independently from halogen selected from F, Cl, Br and I, preferably F, -OH, (C 1 -C 8)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)hydroxyalkyl, m is in each occurrence independently 0 or an integer selected from 1, 2 or 3; R 4 and R 5, the same or different, are selected from the group consisting of -H, (C 1 -C 6)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)hydroxyalkyl, (C 3 -C 6)heterocycloalkyl; R 6 and R 7 are independently selected from the group consisting of -H, (C 1 -C 6)alkyl; wherein, where not already specified, aryl refers to mono, bi- or tri-cyclic ring systems which have 6 to 20 ring atoms, in which at least one ring is aromatic; heteroaryl refers to mono-, bi- or tri-cyclic ring systems with 5 to 20 ring atoms, in which at least one ring is aromatic and in which at least one ring atom is a heteroatom selected from N, S or O; (C 3 -C 6)heterocycloalkyl refers to saturated or partially unsaturated monocyclic (C 3 -C 6)cycloalkyl groups in which at least one ring carbon atom is replaced by at least one heteroatom selected from N, NH, S or O and/or may bear an oxo substituent group; single enantiomers, diastereoisomers and mixtures thereof in any proportion and pharmaceutically acceptable salts and solvates thereof. X 1, X 2, X 3 and X 4 are all CH or one of X 1, X 2, X 3 and X 4 is N and the others are CH; p is zero or an integer from 1 to 4; each R, when present, is in each occurrence independently selected from (C 1 -C 6)alkyl and halogen selected from F, Cl, Br and I; wherein preferably R is F, Cl or methyl; R 1 is pyrimidinyl, preferably pyrimidin-4yl, substituted by one or more group selected from -(CH 2) m NH 2; particularly preferably R 1 is 2-aminopyrimidin-4-yl; L is -C NH- or -NHC -; n is in each occurrence independently 0 or an integer selected from 1, 2 or 3; R 2 and R 3 are in each occurrence independently selected from the group consisting of -H, halogen, -OH, -(CH 2) m NR 4 R 5, (C 1 -C 6)alkyl, (C 1 -C 6)hydroxyalkyl, (C 1 -C 6) alkoxy, (C 1 -C 6) alkoxy (C 1 -C 6)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)haloalkoxy, (C 1 -C 6)haloalkoxy (C 1 -C 6)alkyl, (C 3 -C 10)cycloalkyl, aryl and (C 3 -C 6)heterocycloalkyl, each of which cycloalkyl, aryl and heterocycloalkyl is in its turn optionally and independently substituted with one or more groups selected from halogen, -OH, (C 1 -C 6)alkyl, (C 1 -C 6)hydroxyalkyl, (C 1 -C 6) alkoxy, (C 1 -C 6) alkoxy (C 1 -C 6)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)haloalkoxy, -(CH 2) m NR 4 R 5, -O-(CH 2) m NR 4 R 5, alkanoyl, aryl, heteroaryl, cycloalkyl, aryl-(C 1 -C 6)alkyl, heteroaryl-(C 1 -C 6)alkyl, (C 3 -C 8)heterocycloalkyl, (C 3 -C 8)heterocycloalkyl-(C 1 -C 6)alkyl, (C 3 -C 8)cycloalkyl-(C 1 -C 6)alkyl, each of said aryl, heteroaryl, cycloalkyl, heterocycloalkyl is still further optionally substituted by one or more group selected independently from halogen selected from F, Cl, Br and I, preferably F, -OH, (C 1 -C 8)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)hydroxyalkyl, m is in each occurrence independently 0 or an integer selected from 1, 2 or 3; R 4 and R 5, the same or different, are selected from the group consisting of -H, (C 1 -C 6)alkyl, (C 1 -C 6)haloalkyl, (C 1 -C 6)hydroxyalkyl, (C 3 -C 6)heterocycloalkyl; R 6 and R 7 are independently selected from the group consisting of -H, (C 1 -C 6)alkyl; wherein, where not already specified, aryl refers to mono, bi- or tri-cyclic ring systems which have 6 to 20 ring atoms, in which at least one ring is aromatic; heteroaryl refers to mono-, bi- or tri-cyclic ring systems with 5 to 20 ring atoms, in which at least one ring is aromatic and in which at least one ring atom is a heteroatom selected from N, S or O; (C 3 -C 6)heterocycloalkyl refers to saturated or partially unsaturated monocyclic (C 3 -C 6)cycloalkyl groups in which at least one ring carbon atom is replaced by at least one heteroatom selected from N, NH, S or O and/or may bear an oxo substituent group; single enantiomers, diastereoisomers and mixtures thereof in any proportion and pharmaceutically acceptable salts and solvates thereof.