A compound of the Formula I: or a tautomer, or an individual isomer or a mixture of isomers thereof wherein: Ring T is a bicyclic heteroaryl ring selected from: Ring A represents an optionally substituted 5- or 6-membered aryl or heteroaryl ring, selected from the following: Ring B represents an optionally substituted 5- or 6-membered aryl or heteroaryl ring, selected from the following: L 1 is selected from NR 1 C and C NR 1; R e, at each occurrence, is independently selected from the group consisting of halo, =O, -CN, -NO 2, -R 4, -OR 2, -NR 2 R 3, -C YR 2, -OC YR 2, -NR 2 C YR 2, -SC YR 2, -NR 2 C(=S)YR 2, -OC(=S)YR 2, -C(=S)YR 2, -YC(=NR 3)YR 2, -YP(=O)(YR 4)(YR 4), -Si(R 2) 3, -NR 2 SO 2 R 2, -S r R 2, -SO 2 NR 2 R 3 and -NR 2 SO 2 NR 2 R 3, wherein each Y is independently a bond, -O-, -S- or -NR 3 -; R 1, R 2 and R 3 are independently selected from H, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic and heteroaryl; alternatively, R 2 and R 3, taken together with the atom to which they are attached, form a 5- or 6-membered saturated, partially saturated or unsaturated ring, which contains 0-2 heteroatoms selected from N, O and S r; each occurrence of R 4 is independently selected from alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic and heteroaryl; each of the alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic and heteroaryl moieties is optionally substituted; r is 0, 1 or 2; and s is 0, 1, 2, 3 or 4; wherein each substituent for an unsaturated carbon atom of an aryl or heteroaryl group and for a carbon atom of an alkyl, alkenyl, alkynyl, alkoxy, haloalkyl, cycloalkyl, cycloalkenyl, cycloalkynyl or non-aromatic heterocyclic group being selected from halogen (F, CI, Br or I), -CN, -R 4, -OR 4, -S r R 2, -SO 2 NR 2 R 3, -NR 2 R 3, - YR 2, -O YR 2, -NR 2 YR 2, -S YR 2, -NR 2 C(=S)YR 2, -OC(=S)YR 2, -C(=S)YR 2, -COCOR 2, -COMCOR 2 (where M is a 1-6 carbon alkylene group), -YP(=O)(YR 4)(YR 4), -Si(R 2) 3, -NO 2, NR 2 SO 2 R 2 and -NR 2 SO 2 NR 2 R 3; and in the case of an alkyl, alkenyl, alkynyl, alkoxy, haloalkyl, cycloalkyl, cycloalkenyl, cycloalkynyl or non-aromatic heterocyclic group, substituents also being selected from =O, =S, =NH, =NNR 2 R 3, =NNHC R 2, =NNHCO 2 R 2, and =NNHSO 2 R 2; and with substituents on a nitrogen being selected from R 4, -NR 2 R 3, -C(=O)R 2, -C(=O)OR 2; -C(=O)SR 2, -C(=O)NR 2 R 3, -C(=NR 2)NR 2 R 3, -C(=NR 2)OR 2, -C(=NR 2)R 3,-COCOR 2, -COMCOR 2 (where M is a 1-6 carbon alkylene group), -CN, -SO 2 R 3, S R 3, -P(=O)(YR 2)(YR 2), -NR 2 SO 2 R 3 and -NR 2 SO 2 NR 2 R 3 or, a pharmaceutically acceptable salt thereof, or a solvate thereof. Ring T is a bicyclic heteroaryl ring selected from: Ring A represents an optionally substituted 5- or 6-membered aryl or heteroaryl ring, selected from the following: Ring B represents an optionally substituted 5- or 6-membered aryl or heteroaryl ring, selected from the following: L 1 is selected from NR 1 C and C NR 1; R e, at each occurrence, is independently selected from the group consisting of halo, =O, -CN, -NO 2, -R 4, -OR 2, -NR 2 R 3, -C YR 2, -OC YR 2, -NR 2 C YR 2, -SC YR 2, -NR 2 C(=S)YR 2, -OC(=S)YR 2, -C(=S)YR 2, -YC(=NR 3)YR 2, -YP(=O)(YR 4)(YR 4), -Si(R 2) 3, -NR 2 SO 2 R 2, -S r R 2, -SO 2 NR 2 R 3 and -NR 2 SO 2 NR 2 R 3, wherein each Y is independently a bond, -O-, -S- or -NR 3 -; R 1, R 2 and R 3 are independently selected from H, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic and heteroaryl; alternatively, R 2 and R 3, taken together with the atom to which they are attached, form a 5- or 6-membered saturated, partially saturated or unsaturated ring, which contains 0-2 heteroatoms selected from N, O and S r; each occurrence of R 4 is independently selected from alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic and heteroaryl; each of the alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heterocyclic and heteroaryl moieties is optionally substituted; r is 0, 1 or 2; and s is 0, 1, 2, 3 or 4; wherein each substituent for an unsaturated carbon atom of an aryl or heteroaryl group and for a carbon atom of an alkyl, alkenyl, alkynyl, alkoxy, haloalkyl, cycloalkyl, cycloalkenyl, cycloalkynyl or non-aromatic heterocyclic group being selected from halogen (F, CI, Br or I), -CN, -R 4, -OR 4, -S r R 2, -SO 2 NR 2 R 3, -NR 2 R 3, - YR 2, -O YR 2, -NR 2 YR 2, -S YR 2, -NR 2 C(=S)YR 2, -OC(=S)YR 2, -C(=S)YR 2, -COCOR 2, -COMCOR 2 (where M is a 1-6 carbon alkylene group), -YP(=O)(YR 4)(YR 4), -Si(R 2) 3, -NO 2, NR 2 SO 2 R 2 and -NR 2 SO 2 NR 2 R 3; and in the case of an alkyl, alkenyl, alkynyl, alkoxy, haloalkyl, cycloalkyl, cycloalkenyl, cycloalkynyl or non-aromatic heterocyclic group, substituents also being selected from =O, =S, =NH, =NNR 2 R 3, =NNHC R 2, =NNHCO 2 R 2, and =NNHSO 2 R 2; and with substituents on a nitrogen being selected from R 4, -NR 2 R 3, -C(=O)R 2, -C(=O)OR 2; -C(=O)SR 2, -C(=O)NR 2 R 3, -C(=NR 2)NR 2 R 3, -C(=NR 2)OR 2, -C(=NR 2)R 3,-COCOR 2, -COMCOR 2 (where M is a 1-6 carbon alkylene group), -CN, -SO 2 R 3, S R 3, -P(=O)(YR 2)(YR 2), -NR 2 SO 2 R 3 and -NR 2 SO 2 NR 2 R 3 or, a pharmaceutically acceptable salt thereof, or a solvate thereof.