A compound having the structure: A-L-B wherein A is an E3 ubiquitin ligase protein binding ligand compound of formula I: wherein L is a group which is directly bonded to the compound of formula I and wherein L is a (-CH 2 CH 2 O) b - group, which is directly bonded to the compound of formula I, wherein b is 1 to 10, preferably 1 to 6, more preferably 1 to 4, and particularly 2, 3 or 4, wherein X is C or N, wherein R 1 is a -(CH 2) m Q v group with a covalent C-linked bond to L, a (C 1 -C 4) alkyl group, or a C-linked (C 3 -C 4) heterocyclic group, wherein m is 0, 1 or 2 and v is 0 or 1, wherein when m is 0, v is 1, wherein Q is a (C 3 -C 4)cyclic or (C 3 -C 4)-C-linked nitrogen containing heterocyclic group, wherein one of the ring atoms in the Q group is optionally substituted with a -NHC group or a -C group, wherein said R 1 groups may be optionally substituted by one or more groups independently selected from F, CN or C, wherein R 2a is OH, -CHF 2, -CF 3, NH 2 or F, wherein R 2b is H or F, wherein R 3 and R 4 are independently selected from H, a covalent C-linked, a covalent O-linked, or a covalent C -linked bond to L, R 5 is a -(C 1 -C 3) alkyl group or a covalent C-linked bond to L, wherein Y is wherein Z is CR 6 R 7 R 8 or SR 6 R 7 R 8 R 9 R 10, wherein R 11 is a covalent C-linked bond or a group, wherein R 12 is -C -, -C - or a -C(=)-R 13 group, wherein when Z is CR 6 R 7 R 8, R 6 and R 7 are each independently -(C 1 -C 3) alkyl groups, or wherein R 6 and R 7 together with the C-atom to which they are attached form a -(C 3 -C 4) cycloalkyl group, wherein when Z is CR 6 R 7 R 8, R 8 is a -(C 1 -C 3) alkyl group, a -(CH 2) q R 8∗ group wherein q is 0, 1 or 2, a -C -R 8∗ group, or a -N - R 8∗ group, and wherein R 8∗ is a covalent C-, or N-linked bond to L, or H, or wherein when Z is SR 6 R 7 R 8 R 9 R 10, R 6, R 7, R 8, R 9 and R 10 are each independently selected from: F; or -(C 1 -C 3) alkyl groups, wherein R 13 is H, F or a-(C 1 -C 3) alkyl group, wherein the -(C 1 -C 3) alkyl groups, or -(C 3 -C 4) cycloalkyl groups where present in a Y group are optionally substituted by one or more substituents independently selected from: methyl; OH; or F, and wherein B is a ligand which binds to a target protein or polypeptide which is to be degraded by ubiquitin ligase and is linked to A though a -C-linkage to the L group and B is independently selected from: and or a pharmaceutically acceptable, salt, enantiomer, stereoisomer, hydrate, solvate, or polymorph thereof. wherein X is C or N, wherein R 1 is a -(CH 2) m Q v group with a covalent C-linked bond to L, a (C 1 -C 4) alkyl group, or a C-linked (C 3 -C 4) heterocyclic group, wherein m is 0, 1 or 2 and v is 0 or 1, wherein when m is 0, v is 1, wherein Q is a (C 3 -C 4)cyclic or (C 3 -C 4)-C-linked nitrogen containing heterocyclic group, wherein one of the ring atoms in the Q group is optionally substituted with a -NHC group or a -C group, wherein said R 1 groups may be optionally substituted by one or more groups independently selected from F, CN or C, wherein R 2a is OH, -CHF 2, -CF 3, NH 2 or F, wherein R 2b is H or F, wherein R 3 and R 4 are independently selected from H, a covalent C-linked, a covalent O-linked, or a covalent C -linked bond to L, R 5 is a -(C 1 -C 3) alkyl group or a covalent C-linked bond to L, wherein Y is wherein Z is CR 6 R 7 R 8 or SR 6 R 7 R 8 R 9 R 10, wherein R 11 is a covalent C-linked bond or a group, wherein R 12 is -C -, -C - or a -C(=)-R 13 group, wherein when Z is CR 6 R 7 R 8, R 6 and R 7 are each independently -(C 1 -C 3) alkyl groups, or wherein R 6 and R 7 together with the C-atom to which they are attached form a -(C 3 -C 4) cycloalkyl group, wherein when Z is CR 6 R 7 R 8, R 8 is a -(C 1 -C 3) alkyl group, a -(CH 2) q R 8∗ group wherein q is 0, 1 or 2, a -C -R 8∗ group, or a -N - R 8∗ group, and wherein R 8∗ is a covalent C-, or N-linked bond to L, or H, or wherein when Z is SR 6 R 7 R 8 R 9 R 10, R 6, R 7, R 8, R 9 and R 10 are each independently selected from: F; or -(C 1 -C 3) alkyl groups, wherein R 13 is H, F or a-(C 1 -C 3) alkyl group, wherein the -(C 1 -C 3) alkyl groups, or -(C 3 -C 4) cycloalkyl groups where present in a Y group are optionally substituted by one or more substituents independently selected from: methyl; OH; or F, and wherein B is a ligand which binds to a target protein or polypeptide which is to be degraded by ubiquitin ligase and is linked to A though a -C-linkage to the L group and B is independently selected from: and or a pharmaceutically acceptable, salt, enantiomer, stereoisomer, hydrate, solvate, or polymorph thereof.