A compound of formula, or a pharmaceutically acceptable salt or solvate thereof: wherein A, B, D and E are independently selected from C, N, O, S and Se, but at least one thereof is C and at least one thereof is N; each dashed line may represent a bond; each incidence of R 6 is independently selected from the group consisting of hydrogen, halide, cyano, C 1 -C 6 alkyl, C 1 -C 6 alkylamino, C 1 -C 6 alkylhydroxy, C 3 -C 6 cycloalkyl, alkylphenyl, phenyl, benzyl, C 1 -C 6 ester, C 2 -C 6 alkenyl, C 1 -C 6 trifluoroalkyl and C 1 -C 6 alkoxy, each of which may be optionally substituted, as appropriate, wherein any optional substituent is independently selected from the group consisting of C1-10 alkyl; C3-6 cycloalkyl; hydroxyalkyl; C1-10 alkoxy; C2-10 alkenyl; C2-10 alkynyl; C6-C12 aryl; aryloxy; heteroaryl; heterocyclyl; halo; hydroxyl; halogenated alkyl; amino; alkylamino; arylamino; acyl; amido; CN; NO 2; N 3; CH 2 OH; CONH 2; CONR 24 R 25; CO 2 R 24; CH 2 OR 24; NHCOR 24; NHCO 2 R 24; C1-3 alkylthio; sulfate; sulfonic acid; sulfonate esters; phosphonic acid; phosphate; phosphonate; mono-, di-, or triphosphate esters; trityl; monomethoxytrityl; R 24 SO; R 24 SO 2; CF 3 S; CF 3 SO 2; and trialkylsilyl; wherein R 24 and R 25 are each independently selected from H or C1-10 alkyl; and R 2 is selected from a 2,6-dialkylphenyl, a 2,6-dialkyl-4-halophenyl, a 2,6-dicycloalkylphenyl, a 2,6-dicycloalkyl-4-halophenyl, and: wherein each incidence of Y is independently selected from C, N, S and O, which may be optionally substituted as appropriate, wherein any optional substituent is independently selected from the group consisting of C1-10 alkyl; C3-6 cycloalkyl; hydroxyalkyl; C1-10 alkoxy; C2-10 alkenyl; C2-10 alkynyl; C6-C12 aryl; aryloxy; heteroaryl; heterocyclyl; halo; hydroxyl; halogenated alkyl; amino; alkylamino; arylamino; acyl; amido; CN; NO 2; N 3; CH 2 OH; CONH 2; CONR 24 R 25; CO 2 R 24; CH 2 OR 24; NHCOR 24; NHCO 2 R 24; C1-3 alkylthio; sulfate; sulfonic acid; sulfonate esters; phosphonic acid; phosphate; phosphonate; mono-, di-, or triphosphate esters; trityl; monomethoxytrityl; R 24 SO; R 24 SO 2; CF 3 S; CF 3 SO 2; and trialkylsilyl; wherein R 24 and R 25 are each independently selected from H or C1-10 alkyl; and R 5 is selected from the group consisting of hydrogen, halo, cyano, amide, sulphonamide, acyl, hydroxyl, C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 3 -C 5 cycloalkyl and C 1 -C 6 alkoxy, all of which groups may be optionally substituted, as appropriate, with halo, cyano or C 1 -C 6 alkoxy. wherein A, B, D and E are independently selected from C, N, O, S and Se, but at least one thereof is C and at least one thereof is N; each dashed line may represent a bond; each incidence of R 6 is independently selected from the group consisting of hydrogen, halide, cyano, C 1 -C 6 alkyl, C 1 -C 6 alkylamino, C 1 -C 6 alkylhydroxy, C 3 -C 6 cycloalkyl, alkylphenyl, phenyl, benzyl, C 1 -C 6 ester, C 2 -C 6 alkenyl, C 1 -C 6 trifluoroalkyl and C 1 -C 6 alkoxy, each of which may be optionally substituted, as appropriate, wherein any optional substituent is independently selected from the group consisting of C1-10 alkyl; C3-6 cycloalkyl; hydroxyalkyl; C1-10 alkoxy; C2-10 alkenyl; C2-10 alkynyl; C6-C12 aryl; aryloxy; heteroaryl; heterocyclyl; halo; hydroxyl; halogenated alkyl; amino; alkylamino; arylamino; acyl; amido; CN; NO 2; N 3; CH 2 OH; CONH 2; CONR 24 R 25; CO 2 R 24; CH 2 OR 24; NHCOR 24; NHCO 2 R 24; C1-3 alkylthio; sulfate; sulfonic acid; sulfonate esters; phosphonic acid; phosphate; phosphonate; mono-, di-, or triphosphate esters; trityl; monomethoxytrityl; R 24 SO; R 24 SO 2; CF 3 S; CF 3 SO 2; and trialkylsilyl; wherein R 24 and R 25 are each independently selected from H or C1-10 alkyl; and R 2 is selected from a 2,6-dialkylphenyl, a 2,6-dialkyl-4-halophenyl, a 2,6-dicycloalkylphenyl, a 2,6-dicycloalkyl-4-halophenyl, and: wherein each incidence of Y is independently selected from C, N, S and O, which may be optionally substituted as appropriate, wherein any optional substituent is independently selected from the group consisting of C1-10 alkyl; C3-6 cycloalkyl; hydroxyalkyl; C1-10 alkoxy; C2-10 alkenyl; C2-10 alkynyl; C6-C12 aryl; aryloxy; heteroaryl; heterocyclyl; halo; hydroxyl; halogenated alkyl; amino; alkylamino; arylamino; acyl; amido; CN; NO 2; N 3; CH 2 OH; CONH 2; CONR 24 R 25; CO 2 R 24; CH 2 OR 24; NHCOR 24; NHCO 2 R 24; C1-3 alkylthio; sulfate; sulfonic acid; sulfonate esters; phosphonic acid; phosphate; phosphonate; mono-, di-, or triphosphate esters; trityl; monomethoxytrityl; R 24 SO; R 24 SO 2; CF 3 S; CF 3 SO 2; and trialkylsilyl; wherein R 24 and R 25 are each independently selected from H or C1-10 alkyl; and R 5 is selected from the group consisting of hydrogen, halo, cyano, amide, sulphonamide, acyl, hydroxyl, C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 3 -C 5 cycloalkyl and C 1 -C 6 alkoxy, all of which groups may be optionally substituted, as appropriate, with halo, cyano or C 1 -C 6 alkoxy.